Import png encoder and begin gif

Former-commit-id: 28605ca292741e3de1e36caef5a4a14b5b425618
Former-commit-id: 45c538d36742adbd6487910e0fba74da1cccf30a
Former-commit-id: 2d524bbb0d9835d5688c762b215a612cc8d9d530

src/ImageProcessor/Common/Extensions/ByteExtensions.cs

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+namespace ImageProcessor
+{
+    using System;
+
+    internal static class ByteExtensions
+    {
+        /// <summary>
+        /// Converts a byte array to a new array where each value in the original array is represented 
+        /// by a the specified number of bits.
+        /// </summary>
+        /// <param name="bytes">The bytes to convert from. Cannot be null.</param>
+        /// <param name="bits">The number of bits per value.</param>
+        /// <returns>The resulting <see cref="T:byte[]"/> array. Is never null.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="bytes"/> is null.</exception>
+        /// <exception cref="ArgumentException"><paramref name="bits"/> is less than or equals than zero.</exception>
+        public static byte[] ToArrayByBitsLength(this byte[] bytes, int bits)
+        {
+            Guard.NotNull(bytes, "bytes");
+            Guard.GreaterThan(bits, 0, "bits");
+
+            byte[] result;
+
+            if (bits < 8)
+            {
+                result = new byte[bytes.Length * 8 / bits];
+
+                int factor = (int)Math.Pow(2, bits) - 1;
+                int mask = (0xFF >> (8 - bits));
+                int resultOffset = 0;
+
+                foreach (byte b in bytes)
+                {
+                    for (int shift = 0; shift < 8; shift += bits)
+                    {
+                        int colorIndex = (((b) >> (8 - bits - shift)) & mask) * (255 / factor);
+
+                        result[resultOffset] = (byte)colorIndex;
+
+                        resultOffset++;
+                    }
+                }
+            }
+            else
+            {
+                result = bytes;
+            }
+
+            return result;
+        }
+    }
+}

src/ImageProcessor/Common/Extensions/ComparableExtensions.cs

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+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="ComparableExtensions.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Extension methods for classes that implement <see cref="IComparable{T}" />.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor
+{
+    using System;
+
+    /// <summary>
+    /// Extension methods for classes that implement <see cref="IComparable{T}"/>.
+    /// </summary>
+    internal static class ComparableExtensions
+    {
+        /// <summary>
+        /// Returns value indicating whether the given number is with in the minimum and maximum
+        /// given range.
+        /// </summary>
+        /// <param name="value">The value to to check. </param>
+        /// <param name="min">The minimum range value.</param>
+        /// <param name="max">The maximum range value.</param>
+        /// <typeparam name="T">The <see cref="System.Type"/> to test.</typeparam>
+        /// <returns>
+        /// True if the value falls within the maximum and minimum; otherwise, false.
+        /// </returns>
+        public static bool IsBetween<T>(this T value, T min, T max) where T : IComparable<T>
+        {
+            return (value.CompareTo(min) > 0) && (value.CompareTo(max) < 0);
+        }
+    }
+}

src/ImageProcessor/Common/Helpers/Guard.cs

@@ -0,0 +1,119 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="Guard.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Provides methods to protect against invalid parameters.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor
+{
+    using System;
+    using System.Globalization;
+
+    /// <summary>
+    /// Provides methods to protect against invalid parameters.
+    /// </summary>
+    internal static class Guard
+    {
+        /// <summary>
+        /// Verifies, that the method parameter with specified object value is not null 
+        /// and throws an exception if it is found to be so.
+        /// </summary>
+        /// <param name="target">
+        /// The target object, which cannot be null.
+        /// </param>
+        /// <param name="parameterName">
+        /// The name of the parameter that is to be checked.
+        /// </param>
+        /// <param name="message">
+        /// The error message, if any to add to the exception.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        /// <paramref name="target"/> is null
+        /// </exception>
+        public static void NotNull(object target, string parameterName, string message = "")
+        {
+            if (target == null)
+            {
+                if (string.IsNullOrWhiteSpace(message))
+                {
+                    throw new ArgumentNullException(parameterName, message);
+                }
+
+                throw new ArgumentNullException(parameterName);
+            }
+        }
+
+        /// <summary>
+        /// Verifies, that the string method parameter with specified object value and message
+        /// is not null, not empty and does not contain only blanks and throws an exception 
+        /// if the object is null.
+        /// </summary>
+        /// <param name="target">The target string, which should be checked against being null or empty.</param>
+        /// <param name="parameterName">Name of the parameter.</param>
+        /// <exception cref="ArgumentNullException">
+        /// <paramref name="target"/> is null.
+        /// </exception>
+        /// <exception cref="ArgumentException">
+        /// <paramref name="target"/> is
+        /// empty or contains only blanks.
+        /// </exception>
+        public static void NotNullOrEmpty(string target, string parameterName)
+        {
+            if (target == null)
+            {
+                throw new ArgumentNullException(parameterName);
+            }
+
+            if (string.IsNullOrWhiteSpace(target))
+            {
+                throw new ArgumentException("String parameter cannot be null or empty and cannot contain only blanks.", parameterName);
+            }
+        }
+
+        /// <summary>
+        /// Verifies that the specified value is less than a maximum value
+        /// and throws an exception if it is not.
+        /// </summary>
+        /// <param name="value">The target value, which should be validated.</param>
+        /// <param name="max">The maximum value.</param>
+        /// <param name="parameterName">The name of the parameter that is to be checked.</param>
+        /// <typeparam name="TValue">The type of the value.</typeparam>
+        /// <exception cref="ArgumentException">
+        /// <paramref name="value"/> is greater than the maximum value.
+        /// </exception>
+        public static void LessThan<TValue>(TValue value, TValue max, string parameterName) where TValue : IComparable<TValue>
+        {
+            if (value.CompareTo(max) >= 0)
+            {
+                throw new ArgumentOutOfRangeException(
+                    parameterName,
+                    string.Format(CultureInfo.CurrentCulture, "Value must be less than {0}", max));
+            }
+        }
+
+        /// <summary>
+        /// Verifies that the specified value is greater than a minimum value
+        /// and throws an exception if it is not.
+        /// </summary>
+        /// <param name="value">The target value, which should be validated.</param>
+        /// <param name="min">The minimum value.</param>
+        /// <param name="parameterName">The name of the parameter that is to be checked.</param>
+        /// <typeparam name="TValue">The type of the value.</typeparam>
+        /// <exception cref="ArgumentException">
+        /// <paramref name="value"/> is less than the minimum value.
+        /// </exception>
+        public static void GreaterThan<TValue>(TValue value, TValue min, string parameterName) where TValue : IComparable<TValue>
+        {
+            if (value.CompareTo(min) <= 0)
+            {
+                throw new ArgumentOutOfRangeException(
+                    parameterName,
+                    string.Format(CultureInfo.CurrentCulture, "Value must be greater than {0}", min));
+            }
+        }
+    }
+}

src/ImageProcessor/Common/Helpers/Utils.cs

@@ -0,0 +1,34 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="Utils.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   General utility methods.
+//   TODO: I don't like having classes like this as they turn into a dumping ground. Investigate method usage.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor
+{
+    /// <summary>
+    /// General utility methods.
+    /// TODO: I don't like having classes like this as they turn into a dumping ground. Investigate method usage.
+    /// </summary>
+    internal static class Utils
+    {
+        /// <summary>
+        /// Swaps two references.
+        /// </summary>
+        /// <typeparam name="TRef">The type of the references to swap.</typeparam>
+        /// <param name="lhs">The first reference.</param>
+        /// <param name="rhs">The second reference.</param>
+        public static void Swap<TRef>(ref TRef lhs, ref TRef rhs) where TRef : class
+        {
+            TRef tmp = lhs;
+
+            lhs = rhs;
+            rhs = tmp;
+        }
+    }
+}

src/ImageProcessor/Formats/Gif/DisposalMethod.cs

@@ -0,0 +1,42 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="DisposalMethod.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Provides enumeration for instructing the decoder what to do with the last image
+//   in an animation sequence.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Provides enumeration for instructing the decoder what to do with the last image 
+    /// in an animation sequence.
+    /// </summary>
+    public enum DisposalMethod
+    {
+        /// <summary>
+        /// No disposal specified. The decoder is not required to take any action. 
+        /// </summary>
+        Unspecified = 0,
+
+        /// <summary>
+        /// Do not dispose. The graphic is to be left in place. 
+        /// </summary>
+        NotDispose = 1,
+
+        /// <summary>
+        /// Restore to background color. The area used by the graphic must be restored to
+        /// the background color. 
+        /// </summary>
+        RestoreToBackground = 2,
+
+        /// <summary>
+        /// Restore to previous. The decoder is required to restore the area overwritten by the 
+        /// graphic with what was there prior to rendering the graphic. 
+        /// </summary>
+        RestoreToPrevious = 3
+    }
+}

src/ImageProcessor/Formats/Gif/GifDecoder.cs

@@ -0,0 +1,382 @@
+namespace ImageProcessor.Formats
+{
+    using System;
+    using System.IO;
+
+    public class GifDecoder : IImageDecoder
+    {
+        public static int MaxCommentLength = 1024 * 8;
+
+        public int HeaderSize
+        {
+            get
+            {
+                return 6;
+            }
+        }
+
+        public bool IsSupportedFileExtension(string extension)
+        {
+            if (extension.StartsWith(".")) extension = extension.Substring(1);
+            return extension.Equals("GIF", StringComparison.OrdinalIgnoreCase);
+        }
+
+        public bool IsSupportedFileFormat(byte[] header)
+        {
+            return header.Length >= 6 &&
+                   header[0] == 0x47 && // G
+                   header[1] == 0x49 && // I
+                   header[2] == 0x46 && // F
+                   header[3] == 0x38 && // 8
+                  (header[4] == 0x39 || header[4] == 0x37) && // 9 or 7
+                   header[5] == 0x61;   // a
+        }
+
+        public void Decode(Image image, Stream stream)
+        {
+            new GifDecoderCore().Decode(image, stream);
+        }
+
+        class GifDecoderCore
+        {
+            private const byte ExtensionIntroducer = 0x21;
+            private const byte Terminator = 0;
+            private const byte ImageLabel = 0x2C;
+            private const byte EndIntroducer = 0x3B;
+            private const byte ApplicationExtensionLabel = 0xFF;
+            private const byte CommentLabel = 0xFE;
+            private const byte ImageDescriptorLabel = 0x2C;
+            private const byte PlainTextLabel = 0x01;
+            private const byte GraphicControlLabel = 0xF9;
+
+            private Image _image;
+            private Stream _stream;
+            private GifLogicalScreenDescriptor _descriptor;
+            private byte[] _globalColorTable;
+            private byte[] _currentFrame;
+            private GifGraphicsControlExtension _graphicsControl;
+
+            public void Decode(Image image, Stream stream)
+            {
+                _image = image;
+
+                _stream = stream;
+                _stream.Seek(6, SeekOrigin.Current);
+
+                ReadLogicalScreenDescriptor();
+
+                if (_descriptor.GlobalColorTableFlag == true)
+                {
+                    _globalColorTable = new byte[_descriptor.GlobalColorTableSize * 3];
+
+                    // Read the global color table from the stream
+                    stream.Read(_globalColorTable, 0, _globalColorTable.Length);
+                }
+
+                int nextFlag = stream.ReadByte();
+                while (nextFlag != 0)
+                {
+                    if (nextFlag == ImageLabel)
+                    {
+                        ReadFrame();
+                    }
+                    else if (nextFlag == ExtensionIntroducer)
+                    {
+                        int gcl = stream.ReadByte();
+                        switch (gcl)
+                        {
+                            case GraphicControlLabel:
+                                ReadGraphicalControlExtension();
+                                break;
+                            case CommentLabel:
+                                ReadComments();
+                                break;
+                            case ApplicationExtensionLabel:
+                                Skip(12);
+                                break;
+                            case PlainTextLabel:
+                                Skip(13);
+                                break;
+                        }
+                    }
+                    else if (nextFlag == EndIntroducer)
+                    {
+                        break;
+                    }
+                    nextFlag = stream.ReadByte();
+                }
+            }
+
+            private void ReadGraphicalControlExtension()
+            {
+                byte[] buffer = new byte[6];
+
+                _stream.Read(buffer, 0, buffer.Length);
+
+                byte packed = buffer[1];
+
+                _graphicsControl = new GifGraphicsControlExtension();
+                _graphicsControl.DelayTime = BitConverter.ToInt16(buffer, 2);
+                _graphicsControl.TransparencyIndex = buffer[4];
+                _graphicsControl.TransparencyFlag = (packed & 0x01) == 1;
+                _graphicsControl.DisposalMethod = (DisposalMethod)((packed & 0x1C) >> 2);
+            }
+
+            private GifImageDescriptor ReadImageDescriptor()
+            {
+                byte[] buffer = new byte[9];
+
+                _stream.Read(buffer, 0, buffer.Length);
+
+                byte packed = buffer[8];
+
+                GifImageDescriptor imageDescriptor = new GifImageDescriptor();
+                imageDescriptor.Left = BitConverter.ToInt16(buffer, 0);
+                imageDescriptor.Top = BitConverter.ToInt16(buffer, 2);
+                imageDescriptor.Width = BitConverter.ToInt16(buffer, 4);
+                imageDescriptor.Height = BitConverter.ToInt16(buffer, 6);
+                imageDescriptor.LocalColorTableFlag = ((packed & 0x80) >> 7) == 1;
+                imageDescriptor.LocalColorTableSize = 2 << (packed & 0x07);
+                imageDescriptor.InterlaceFlag = ((packed & 0x40) >> 6) == 1;
+
+                return imageDescriptor;
+            }
+
+            private void ReadLogicalScreenDescriptor()
+            {
+                byte[] buffer = new byte[7];
+
+                _stream.Read(buffer, 0, buffer.Length);
+
+                byte packed = buffer[4];
+
+                _descriptor = new GifLogicalScreenDescriptor();
+                _descriptor.Width = BitConverter.ToInt16(buffer, 0);
+                _descriptor.Height = BitConverter.ToInt16(buffer, 2);
+                _descriptor.Background = buffer[5];
+                _descriptor.GlobalColorTableFlag = ((packed & 0x80) >> 7) == 1;
+                _descriptor.GlobalColorTableSize = 2 << (packed & 0x07);
+
+                if (_descriptor.GlobalColorTableSize > 255 * 4)
+                {
+                    throw new ImageFormatException(string.Format("Invalid gif colormap size '{0}'", _descriptor.GlobalColorTableSize));
+                }
+
+                if (_descriptor.Width > ImageBase.MaxWidth || _descriptor.Height > ImageBase.MaxHeight)
+                {
+                    throw new ArgumentOutOfRangeException(
+                        string.Format("The input gif '{0}x{1}' is bigger then the max allowed size '{2}x{3}'",
+                         _descriptor.Width,
+                          _descriptor.Height,
+                          ImageBase.MaxWidth,
+                           ImageBase.MaxHeight));
+                }
+            }
+
+            private void Skip(int length)
+            {
+                _stream.Seek(length, SeekOrigin.Current);
+
+                int flag = 0;
+
+                while ((flag = _stream.ReadByte()) != 0)
+                {
+                    _stream.Seek(flag, SeekOrigin.Current);
+                }
+            }
+
+            private void ReadComments()
+            {
+                int flag = 0;
+
+                while ((flag = _stream.ReadByte()) != 0)
+                {
+                    if (flag > MaxCommentLength)
+                    {
+                        throw new ImageFormatException(string.Format("Gif comment length '{0}' exceeds max '{1}'", flag, MaxCommentLength));
+                    }
+
+                    byte[] buffer = new byte[flag];
+
+                    _stream.Read(buffer, 0, flag);
+
+                    _image.Properties.Add(new ImageProperty("Comments", BitConverter.ToString(buffer)));
+                }
+            }
+
+            private void ReadFrame()
+            {
+                GifImageDescriptor imageDescriptor = ReadImageDescriptor();
+
+                byte[] localColorTable = ReadFrameLocalColorTable(imageDescriptor);
+
+                byte[] indices = ReadFrameIndices(imageDescriptor);
+
+                // Determine the color table for this frame. If there is a local one, use it
+                // otherwise use the global color table.
+                byte[] colorTable = localColorTable ?? this._globalColorTable;
+
+                ReadFrameColors(indices, colorTable, imageDescriptor);
+
+                Skip(0); // skip any remaining blocks
+            }
+
+            private byte[] ReadFrameIndices(GifImageDescriptor imageDescriptor)
+            {
+                int dataSize = _stream.ReadByte();
+
+                LzwDecoder lzwDecoder = new LzwDecoder(_stream);
+
+                byte[] indices = lzwDecoder.DecodePixels(imageDescriptor.Width, imageDescriptor.Height, dataSize);
+                return indices;
+            }
+
+            private byte[] ReadFrameLocalColorTable(GifImageDescriptor imageDescriptor)
+            {
+                byte[] localColorTable = null;
+
+                if (imageDescriptor.LocalColorTableFlag)
+                {
+                    localColorTable = new byte[imageDescriptor.LocalColorTableSize * 3];
+
+                    _stream.Read(localColorTable, 0, localColorTable.Length);
+                }
+
+                return localColorTable;
+            }
+
+            private void ReadFrameColors(byte[] indices, byte[] colorTable, GifImageDescriptor descriptor)
+            {
+                int imageWidth = _descriptor.Width;
+                int imageHeight = _descriptor.Height;
+
+                if (_currentFrame == null)
+                {
+                    _currentFrame = new byte[imageWidth * imageHeight * 4];
+                }
+
+                byte[] lastFrame = null;
+
+                if (_graphicsControl != null &&
+                    _graphicsControl.DisposalMethod == DisposalMethod.RestoreToPrevious)
+                {
+                    lastFrame = new byte[imageWidth * imageHeight * 4];
+
+                    Array.Copy(_currentFrame, lastFrame, lastFrame.Length);
+                }
+
+                int offset = 0, i = 0, index = -1;
+
+                int iPass = 0; // the interlace pass
+                int iInc = 8; // the interlacing line increment
+                int iY = 0; // the current interlaced line
+                int writeY = 0; // the target y offset to write to
+
+                for (int y = descriptor.Top; y < descriptor.Top + descriptor.Height; y++)
+                {
+                    // Check if this image is interlaced.
+                    if (descriptor.InterlaceFlag)
+                    {
+                        // If so then we read lines at predetermined offsets.
+                        // When an entire image height worth of offset lines has been read we consider this a pass.
+                        // With each pass the number of offset lines changes and the starting line changes.
+                        if (iY >= descriptor.Height)
+                        {
+                            iPass++;
+                            switch (iPass)
+                            {
+                                case 1:
+                                    iY = 4;
+                                    break;
+                                case 2:
+                                    iY = 2;
+                                    iInc = 4;
+                                    break;
+                                case 3:
+                                    iY = 1;
+                                    iInc = 2;
+                                    break;
+                            }
+                        }
+
+                        writeY = iY + descriptor.Top;
+
+                        iY += iInc;
+                    }
+                    else
+                    {
+                        writeY = y;
+                    }
+
+                    for (int x = descriptor.Left; x < descriptor.Left + descriptor.Width; x++)
+                    {
+                        offset = writeY * imageWidth + x;
+
+                        index = indices[i];
+
+                        if (_graphicsControl == null ||
+                            _graphicsControl.TransparencyFlag == false ||
+                            _graphicsControl.TransparencyIndex != index)
+                        {
+                            _currentFrame[offset * 4 + 0] = colorTable[index * 3 + 2];
+                            _currentFrame[offset * 4 + 1] = colorTable[index * 3 + 1];
+                            _currentFrame[offset * 4 + 2] = colorTable[index * 3 + 0];
+                            _currentFrame[offset * 4 + 3] = (byte)255;
+                        }
+
+                        i++;
+                    }
+                }
+
+                byte[] pixels = new byte[imageWidth * imageHeight * 4];
+
+                Array.Copy(_currentFrame, pixels, pixels.Length);
+
+                ImageBase currentImage = null;
+
+                if (_image.Pixels == null)
+                {
+                    currentImage = _image;
+                    currentImage.SetPixels(imageWidth, imageHeight, pixels);
+
+                    if (_graphicsControl != null && _graphicsControl.DelayTime > 0)
+                    {
+                        _image.DelayTime = _graphicsControl.DelayTime;
+                    }
+                }
+                else
+                {
+                    ImageFrame frame = new ImageFrame();
+
+                    currentImage = frame;
+                    currentImage.SetPixels(imageWidth, imageHeight, pixels);
+
+                    _image.Frames.Add(frame);
+                }
+
+                if (_graphicsControl != null)
+                {
+                    if (_graphicsControl.DisposalMethod == DisposalMethod.RestoreToBackground)
+                    {
+                        for (int y = descriptor.Top; y < descriptor.Top + descriptor.Height; y++)
+                        {
+                            for (int x = descriptor.Left; x < descriptor.Left + descriptor.Width; x++)
+                            {
+                                offset = y * imageWidth + x;
+
+                                _currentFrame[offset * 4 + 0] = 0;
+                                _currentFrame[offset * 4 + 1] = 0;
+                                _currentFrame[offset * 4 + 2] = 0;
+                                _currentFrame[offset * 4 + 3] = 0;
+                            }
+                        }
+                    }
+                    else if (_graphicsControl.DisposalMethod == DisposalMethod.RestoreToPrevious)
+                    {
+                        _currentFrame = lastFrame;
+                    }
+                }
+            }
+        }
+    }
+}

src/ImageProcessor/Formats/Gif/GifGraphicsControlExtension.cs

@@ -0,0 +1,49 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="GifGraphicsControlExtension.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   The Graphic Control Extension contains parameters used when
+//   processing a graphic rendering block.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// The Graphic Control Extension contains parameters used when 
+    /// processing a graphic rendering block.
+    /// </summary>
+    internal sealed class GifGraphicsControlExtension
+    {
+        /// <summary>
+        /// Gets or sets the disposal method which indicates the way in which the 
+        /// graphic is to be treated after being displayed. 
+        /// </summary>
+        public DisposalMethod DisposalMethod { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether transparency flag is to be set.
+        /// This indicates whether a transparency index is given in the Transparent Index field. 
+        /// (This field is the least significant bit of the byte.) 
+        /// </summary>
+        public bool TransparencyFlag { get; set; }
+
+        /// <summary>
+        /// Gets or sets the transparency index.
+        /// The Transparency Index is such that when encountered, the corresponding pixel 
+        /// of the display device is not modified and processing goes on to the next pixel.
+        /// </summary>
+        public int TransparencyIndex { get; set; }
+
+        /// <summary>
+        /// Gets or sets the delay time.
+        /// If not 0, this field specifies the number of hundredths (1/100) of a second to 
+        /// wait before continuing with the processing of the Data Stream. 
+        /// The clock starts ticking immediately after the graphic is rendered. 
+        /// This field may be used in conjunction with the User Input Flag field. 
+        /// </summary>
+        public int DelayTime { get; set; }
+    }
+}

src/ImageProcessor/Formats/Gif/GifImageDescriptor.cs

@@ -0,0 +1,72 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="GifImageDescriptor.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Each image in the Data Stream is composed of an Image Descriptor,
+//   an optional Local Color Table, and the image data.
+//   Each image must fit within the boundaries of the
+//   Logical Screen, as defined in the Logical Screen Descriptor.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Each image in the Data Stream is composed of an Image Descriptor, 
+    /// an optional Local Color Table, and the image data. 
+    /// Each image must fit within the boundaries of the 
+    /// Logical Screen, as defined in the Logical Screen Descriptor. 
+    /// </summary>
+    internal sealed class GifImageDescriptor
+    {
+        /// <summary>
+        /// Gets or sets the column number, in pixels, of the left edge of the image, 
+        /// with respect to the left edge of the Logical Screen. 
+        /// Leftmost column of the Logical Screen is 0.
+        /// </summary>
+        public short Left { get; set; }
+
+        /// <summary>
+        /// Gets or sets the row number, in pixels, of the top edge of the image with 
+        /// respect to the top edge of the Logical Screen. 
+        /// Top row of the Logical Screen is 0.
+        /// </summary>
+        public short Top { get; set; }
+
+
+        /// <summary>
+        /// Gets or sets the width of the image in pixels.
+        /// </summary>
+        public short Width { get; set; }
+
+
+        /// <summary>
+        /// Gets or sets the height of the image in pixels.
+        /// </summary>
+        public short Height { get; set; }
+
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the presence of a Local Color Table immediately 
+        /// follows this Image Descriptor.
+        /// </summary>
+        public bool LocalColorTableFlag { get; set; }
+
+
+        /// <summary>
+        /// Gets or sets the local color table size.
+        /// If the Local Color Table Flag is set to 1, the value in this field 
+        /// is used to calculate the number of bytes contained in the Local Color Table.
+        /// </summary>
+        public int LocalColorTableSize { get; set; }
+
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the image is to be interlaced. 
+        /// An image is interlaced in a four-pass interlace pattern.
+        /// </summary>
+        public bool InterlaceFlag { get; set; }
+    }
+}

src/ImageProcessor/Formats/Gif/GifLogicalScreenDescriptor.cs

@@ -0,0 +1,57 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="GifLogicalScreenDescriptor.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   The Logical Screen Descriptor contains the parameters
+//   necessary to define the area of the display device
+//   within which the images will be rendered
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// The Logical Screen Descriptor contains the parameters 
+    /// necessary to define the area of the display device 
+    /// within which the images will be rendered
+    /// </summary>
+    internal sealed class GifLogicalScreenDescriptor
+    {
+        /// <summary>
+        /// Gets or sets the width, in pixels, of the Logical Screen where the images will 
+        /// be rendered in the displaying device.
+        /// </summary>
+        public short Width { get; set; }
+
+        /// <summary>
+        /// Gets or sets the height, in pixels, of the Logical Screen where the images will be 
+        /// rendered in the displaying device.
+        /// </summary>
+        public short Height { get; set; }
+
+        /// <summary>
+        /// Gets or sets the index at the Global Color Table for the Background Color. 
+        /// The Background Color is the color used for those 
+        /// pixels on the screen that are not covered by an image.
+        /// </summary>
+        public byte Background { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether a flag denoting the presence of a Global Color Table
+        /// should be set. 
+        /// If the flag is set, the Global Color Table will immediately 
+        /// follow the Logical Screen Descriptor.
+        /// </summary>
+        public bool GlobalColorTableFlag { get; set; }
+
+        /// <summary>
+        /// Gets or sets the global color table size.
+        /// If the Global Color Table Flag is set to 1, 
+        /// the value in this field is used to calculate the number of 
+        /// bytes contained in the Global Color Table.
+        /// </summary>
+        public int GlobalColorTableSize { get; set; }
+    }
+}

src/ImageProcessor/Formats/Gif/LzwDecoder.cs

@@ -0,0 +1,270 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="LzwDecoder.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Decompresses data using the LZW algorithms.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System;
+    using System.IO;
+
+    /// <summary>
+    /// Decompresses data using the LZW algorithms.
+    /// </summary>
+    internal sealed class LzwDecoder
+    {
+        /// <summary>
+        /// The stack size.
+        /// </summary>
+        private const int StackSize = 4096;
+
+        /// <summary>
+        /// The null code.
+        /// </summary>
+        private const int NullCode = -1;
+
+        /// <summary>
+        /// The stream.
+        /// </summary>
+        private readonly Stream stream;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LzwDecoder"/> class
+        /// and sets the stream, where the compressed data should be read from.
+        /// </summary>
+        /// <param name="stream">The stream. where to read from.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="stream"/> is null
+        /// (Nothing in Visual Basic).</exception>
+        public LzwDecoder(Stream stream)
+        {
+            Guard.NotNull(stream, "stream");
+
+            this.stream = stream;
+        }
+
+        /// <summary>
+        /// Decodes and decompresses all pixel indices from the stream.
+        /// </summary>
+        /// <param name="width">The width of the pixel index array.</param>
+        /// <param name="height">The height of the pixel index array.</param>
+        /// <param name="dataSize">Size of the data.</param>
+        /// <returns>The decoded and uncompressed array.</returns>
+        public byte[] DecodePixels(int width, int height, int dataSize)
+        {
+            Guard.LessThan(dataSize, int.MaxValue, "dataSize");
+
+            // The resulting index table.
+            byte[] pixels = new byte[width * height];
+
+            // Calculate the clear code. The value of the clear code is 2 ^ dataSize
+            int clearCode = 1 << dataSize;
+
+            int codeSize = dataSize + 1;
+
+            // Calculate the end code
+            int endCode = clearCode + 1;
+
+            // Calculate the available code.
+            int availableCode = clearCode + 2;
+
+            #region Jillzhangs Code (Not From Me) see: http://giflib.codeplex.com/
+            // TODO: It's imperative that this close is cleaned up and commented properly.
+            // TODO: Unfortunately I can't figure out the character encoding to translate from the original Chinese. 
+            int code; // ÓÃÓÚ´æ´¢µ±Ç°µÄ±àÂëÖµ
+            int oldCode = NullCode; // ÓÃÓÚ´æ´¢ÉÏÒ»´ÎµÄ±àÂëÖµ
+            int codeMask = (1 << codeSize) - 1; // ±íʾ±àÂëµÄ×î´óÖµ£¬Èç¹ûcodeSize=5,Ôòcode_mask=31
+            int bits = 0; // ÔÚ±àÂëÁ÷ÖÐÊý¾ÝµÄ±£´æÐÎʽΪbyte£¬¶øʵ¼Ê±àÂë¹ý³ÌÖÐÊÇÕÒʵ¼Ê±àÂëλÀ´´æ´¢µÄ£¬±ÈÈçµ±codeSize=5µÄʱºò£¬ÄÇôʵ¼ÊÉÏ5bitµÄÊý¾Ý¾ÍÓ¦¸Ã¿ÉÒÔ±íʾһ¸ö±àÂ룬ÕâÑùÈ¡³öÀ´µÄ1¸ö×ֽھ͸»ÓàÁË3¸öbit£¬Õâ3¸öbitÓÃÓں͵ڶþ¸ö×ֽڵĺóÁ½¸öbit½øÐÐ×éºÏ£¬ÔÙ´ÎÐγɱàÂëÖµ£¬Èç´ËÀàÍÆ
+
+
+            int[] prefix = new int[StackSize]; // ÓÃÓÚ±£´æǰ׺µÄ¼¯ºÏ
+            int[] suffix = new int[StackSize]; // ÓÃÓÚ±£´æºó׺
+            int[] pixelStatck = new int[StackSize + 1]; // ÓÃÓÚÁÙʱ±£´æÊý¾ÝÁ÷
+
+            int top = 0;
+            int count = 0; // ÔÚÏÂÃæµÄÑ­»·ÖУ¬Ã¿´Î»á»ñÈ¡Ò»¶¨Á¿µÄ±àÂëµÄ×Ö½ÚÊý×飬¶ø´¦ÀíÕâЩÊý×éµÄʱºòÐèÒª1¸ö¸ö×Ö½ÚÀ´´¦Àí£¬count¾ÍÊDZíʾ»¹Òª´¦ÀíµÄ×Ö½ÚÊýÄ¿
+            int bi = 0; // count±íʾ»¹Ê£¶àÉÙ×Ö½ÚÐèÒª´¦Àí£¬¶øbiÔò±íʾ±¾´ÎÒѾ­´¦ÀíµÄ¸öÊý
+            int xyz = 0; // i´ú±íµ±Ç°´¦ÀíµÃµ½ÏñËØÊý
+
+            int data = 0; // ±íʾµ±Ç°´¦ÀíµÄÊý¾ÝµÄÖµ
+            int first = 0; // Ò»¸ö×Ö·û´®ÖصĵÚÒ»¸ö×Ö½Ú
+            int inCode; // ÔÚlzwÖУ¬Èç¹ûÈÏʶÁËÒ»¸ö±àÂëËù´ú±íµÄÊý¾Ýentry£¬Ôò½«±àÂë×÷ΪÏÂÒ»´ÎµÄprefix£¬´Ë´¦inCode´ú±í´«µÝ¸øÏÂÒ»´Î×÷Ϊǰ׺µÄ±àÂëÖµ
+
+            // ÏÈÉú³ÉÔªÊý¾ÝµÄǰ׺¼¯ºÏºÍºó׺¼¯ºÏ£¬ÔªÊý¾ÝµÄǰ׺¾ùΪ0£¬¶øºó׺ÓëÔªÊý¾ÝÏàµÈ£¬Í¬Ê±±àÂëÒ²ÓëÔªÊý¾ÝÏàµÈ
+            for (code = 0; code < clearCode; code++)
+            {
+                // ǰ׺³õʼΪ0
+                prefix[code] = 0;
+
+                // ºó׺=ÔªÊý¾Ý=±àÂë
+                suffix[code] = (byte)code;
+            }
+
+            byte[] buffer = null;
+            while (xyz < pixels.Length)
+            {
+                // ×î´óÏñËØÊýÒѾ­È·¶¨ÎªpixelCount = width * width
+                if (top == 0)
+                {
+                    if (bits < codeSize)
+                    {
+                        // Èç¹ûµ±Ç°µÄÒª´¦ÀíµÄbitÊýСÓÚ±àÂëλ´óС£¬ÔòÐèÒª¼ÓÔØÊý¾Ý
+                        if (count == 0)
+                        {
+                            // Èç¹ûcountΪ0£¬±íʾҪ´Ó±àÂëÁ÷ÖжÁÒ»¸öÊý¾Ý¶ÎÀ´½øÐзÖÎö
+                            buffer = this.ReadBlock();
+                            count = buffer.Length;
+                            if (count == 0)
+                            {
+                                // ÔÙ´ÎÏë¶ÁÈ¡Êý¾Ý¶Î£¬È´Ã»ÓжÁµ½Êý¾Ý£¬´Ëʱ¾Í±íÃ÷ÒѾ­´¦ÀíÍêÁË
+                                break;
+                            }
+
+                            // ÖØжÁÈ¡Ò»¸öÊý¾Ý¶Îºó£¬Ó¦¸Ã½«ÒѾ­´¦ÀíµÄ¸öÊýÖÃ0
+                            bi = 0;
+                        }
+
+                        // »ñÈ¡±¾´ÎÒª´¦ÀíµÄÊý¾ÝµÄÖµ
+                        data += buffer[bi] << bits; // ´Ë´¦ÎªºÎÒªÒÆλÄØ£¬±ÈÈçµÚÒ»´Î´¦ÀíÁË1¸ö×Ö½ÚΪ176£¬µÚÒ»´ÎÖ»Òª´¦Àí5bit¾Í¹»ÁË£¬Ê£ÏÂ3bitÁô¸øϸö×Ö½Ú½øÐÐ×éºÏ¡£Ò²¾ÍÊǵڶþ¸ö×ֽڵĺóÁ½Î»+µÚÒ»¸ö×Ö½ÚµÄÇ°Èýλ×é³ÉµÚ¶þ´ÎÊä³öÖµ
+                        bits += 8; // ±¾´ÎÓÖ´¦ÀíÁËÒ»¸ö×Ö½Ú£¬ËùÒÔÐèÒª+8                    
+                        bi++; // ½«´¦ÀíÏÂÒ»¸ö×Ö½Ú
+                        count--; // ÒѾ­´¦Àí¹ýµÄ×Ö½ÚÊý+1
+                        continue;
+                    }
+
+                    // Èç¹ûÒѾ­ÓÐ×ã¹»µÄbitÊý¿É¹©´¦Àí£¬ÏÂÃæ¾ÍÊÇ´¦Àí¹ý³Ì
+                    // »ñÈ¡±àÂë
+                    code = data & codeMask; // »ñÈ¡dataÊý¾ÝµÄ±àÂëλ´óСbitµÄÊý¾Ý
+                    data >>= codeSize; // ½«±àÂëÊý¾Ý½ØÈ¡ºó£¬Ô­À´µÄÊý¾Ý¾Íʣϼ¸¸öbitÁË£¬´Ëʱ½«ÕâЩbitÓÒÒÆ£¬ÎªÏ´Î×÷×¼±¸
+                    bits -= codeSize; // ͬʱÐèÒª½«µ±Ç°Êý¾ÝµÄbitÊý¼õÈ¥±àÂë볤£¬ÒòΪÒѾ­µÃµ½ÁË´¦Àí¡£
+
+                    // ÏÂÃæ¸ù¾Ý»ñÈ¡µÄcodeÖµÀ´½øÐд¦Àí
+                    if (code > availableCode || code == endCode)
+                    {
+                        // µ±±àÂëÖµ´óÓÚ×î´ó±àÂëÖµ»òÕßΪ½áÊø±ê¼ÇµÄʱºò£¬Í£Ö¹´¦Àí                     
+                        break;
+                    }
+
+                    if (code == clearCode)
+                    {
+                        // Èç¹ûµ±Ç°ÊÇÇå³ý±ê¼Ç£¬ÔòÖØгõʼ»¯±äÁ¿£¬ºÃÖØÐÂÔÙÀ´
+                        codeSize = dataSize + 1;
+
+                        // ÖØгõʼ»¯×î´ó±àÂëÖµ
+                        codeMask = (1 << codeSize) - 1;
+
+                        // ³õʼ»¯ÏÂÒ»²½Ó¦¸Ã´¦ÀíµÃ±àÂëÖµ
+                        availableCode = clearCode + 2;
+
+                        // ½«±£´æµ½old_codeÖеÄÖµÇå³ý£¬ÒÔ±ãÖØÍ·ÔÙÀ´
+                        oldCode = NullCode;
+                        continue;
+                    }
+
+                    // ÏÂÃæÊÇcodeÊôÓÚÄÜѹËõµÄ±àÂ뷶ΧÄڵĵĴ¦Àí¹ý³Ì
+                    if (oldCode == NullCode)
+                    {
+                        // Èç¹ûµ±Ç°±àÂëֵΪ¿Õ,±íʾÊǵÚÒ»´Î»ñÈ¡±àÂë
+                        pixelStatck[top++] = suffix[code]; // »ñÈ¡µ½1¸öÊý¾ÝÁ÷µÄÊý¾Ý
+
+                        // ±¾´Î±àÂë´¦ÀíÍê³É£¬½«±àÂëÖµ±£´æµ½old_codeÖÐ
+                        oldCode = code;
+
+                        // µÚÒ»¸ö×Ö·ûΪµ±Ç°±àÂë
+                        first = code;
+                        continue;
+                    }
+
+                    inCode = code;
+                    if (code == availableCode)
+                    {
+                        // Èç¹ûµ±Ç°±àÂëºÍ±¾´ÎÓ¦¸ÃÉú³ÉµÄ±àÂëÏàͬ
+                        // ÄÇôÏÂÒ»¸öÊý¾Ý×ֽھ͵ÈÓÚµ±Ç°´¦Àí×Ö·û´®µÄµÚÒ»¸ö×Ö½Ú
+                        pixelStatck[top++] = (byte)first;
+
+                        code = oldCode; // »ØËݵ½ÉÏÒ»¸ö±àÂë
+                    }
+
+                    while (code > clearCode)
+                    {
+                        // Èç¹ûµ±Ç°±àÂë´óÓÚÇå³ý±ê¼Ç£¬±íʾ±àÂëÖµÊÇÄÜѹËõÊý¾ÝµÄ
+                        pixelStatck[top++] = suffix[code];
+                        code = prefix[code]; // »ØËݵ½ÉÏÒ»¸ö±àÂë
+                    }
+
+                    first = suffix[code];
+
+                    // »ñÈ¡ÏÂÒ»¸öÊý¾Ý
+                    pixelStatck[top++] = suffix[code];
+
+                    // Fix for Gifs that have "deferred clear code" as per here : https://bugzilla.mozilla.org/show_bug.cgi?id=55918
+                    if (availableCode < StackSize)
+                    {
+                        // ÉèÖõ±Ç°Ó¦¸Ã±àÂëλÖõÄǰ׺
+                        prefix[availableCode] = oldCode;
+
+                        // ÉèÖõ±Ç°Ó¦¸Ã±àÂëλÖõĺó׺
+                        suffix[availableCode] = first;
+
+                        // Ï´ÎÓ¦¸ÃµÃµ½µÄ±àÂëÖµ
+                        availableCode++;
+                        if (availableCode == codeMask + 1 && availableCode < StackSize)
+                        {
+                            // Ôö¼Ó±àÂëλÊý
+                            codeSize++;
+
+                            // ÖØÉè×î´ó±àÂëÖµ
+                            codeMask = (1 << codeSize) - 1;
+                        }
+                    }
+
+                    // »¹Ô­old_code
+                    oldCode = inCode;
+                }
+
+                // »ØËݵ½ÉÏÒ»¸ö´¦ÀíλÖÃ
+                top--;
+
+                // »ñÈ¡ÔªÊý¾Ý              
+                pixels[xyz++] = (byte)pixelStatck[top];
+            }
+
+            #endregion
+
+            return pixels;
+        }
+
+        /// <summary>
+        /// Reads the next data block from the stream. A data block begins with a byte,
+        /// which defines the size of the block, followed by the block itself.
+        /// </summary>
+        /// <returns>
+        /// The <see cref="T:byte[]"/>.
+        /// </returns>
+        private byte[] ReadBlock()
+        {
+            int blockSize = this.stream.ReadByte();
+            return this.ReadBytes(blockSize);
+        }
+
+        /// <summary>
+        /// Reads the specified number of bytes from the data stream.
+        /// </summary>
+        /// <param name="length">
+        /// The number of bytes to read.
+        /// </param>
+        /// <returns>
+        /// The <see cref="T:byte[]"/>.
+        /// </returns>
+        private byte[] ReadBytes(int length)
+        {
+            byte[] buffer = new byte[length];
+            this.stream.Read(buffer, 0, length);
+            return buffer;
+        }
+    }
+}

src/ImageProcessor/Formats/IImageDecoder.cs

@@ -0,0 +1,53 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="IImageDecoder.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Encapsulates properties and methods required for decoding an image from a stream.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System.IO;
+
+    /// <summary>
+    /// Encapsulates properties and methods required for decoding an image from a stream.
+    /// </summary>
+    public interface IImageDecoder
+    {
+        /// <summary>
+        /// Gets the size of the header for this image type.
+        /// </summary>
+        /// <value>The size of the header.</value>
+        int HeaderSize { get; }
+
+        /// <summary>
+        /// Returns a value indicating whether the <see cref="IImageDecoder"/> supports the specified
+        /// file header.
+        /// </summary>
+        /// <param name="extension">The <see cref="string"/> containing the file extension.</param>
+        /// <returns>
+        /// True if the decoder supports the file extension; otherwise, false.
+        /// </returns>
+        bool IsSupportedFileExtension(string extension);
+
+        /// <summary>
+        /// Returns a value indicating whether the <see cref="IImageDecoder"/> supports the specified
+        /// file header.
+        /// </summary>
+        /// <param name="header">The <see cref="T:byte[]"/> containing the file header.</param>
+        /// <returns>
+        /// True if the decoder supports the file header; otherwise, false.
+        /// </returns>
+        bool IsSupportedFileFormat(byte[] header);
+
+        /// <summary>
+        /// Decodes the image from the specified stream to the <see cref="ImageBase"/>.
+        /// </summary>
+        /// <param name="image">The <see cref="ImageBase"/> to decode to.</param>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        void Decode(Image image, Stream stream);
+    }
+}

src/ImageProcessor/Formats/IImageEncoder.cs

@@ -0,0 +1,47 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="IImageEncoder.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Encapsulates properties and methods required for decoding an image to a stream.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System.IO;
+
+    /// <summary>
+    /// Encapsulates properties and methods required for encoding an image to a stream.
+    /// </summary>
+    public interface IImageEncoder
+    {
+        /// <summary>
+        /// Gets or sets the quality of output for images.
+        /// </summary>
+        int Quality { get; set; }
+
+        /// <summary>
+        /// Gets the default file extension for this encoder.
+        /// </summary>
+        string Extension { get; }
+
+        /// <summary>
+        /// Returns a value indicating whether the <see cref="IImageEncoder"/> supports the specified
+        /// file header.
+        /// </summary>
+        /// <param name="extension">The <see cref="string"/> containing the file extension.</param>
+        /// <returns>
+        /// True if the decoder supports the file extension; otherwise, false.
+        /// </returns>
+        bool IsSupportedFileExtension(string extension);
+
+        /// <summary>
+        /// Encodes the image to the specified stream from the <see cref="ImageBase"/>.
+        /// </summary>
+        /// <param name="image">The <see cref="ImageBase"/> to encode from.</param>
+        /// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
+        void Encode(ImageBase image, Stream stream);
+    }
+}

src/ImageProcessor/Formats/IImageFormat.cs

@@ -0,0 +1,9 @@
+namespace ImageProcessor.Encoders
+{
+    public interface IImageFormat
+    {
+        IImageEncoder Encoder { get; }
+
+        IImageDecoder Decoder { get; }
+    }
+}

src/ImageProcessor/Formats/Png/GrayscaleReader.cs

@@ -0,0 +1,83 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="GrayscaleReader.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Color reader for reading grayscale colors from a png file.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Color reader for reading grayscale colors from a png file.
+    /// </summary>
+    public sealed class GrayscaleReader : IColorReader
+    {
+        /// <summary>
+        /// Whether t also read the alpha channel.
+        /// </summary>
+        private readonly bool useAlpha;
+
+        /// <summary>
+        /// The current row.
+        /// </summary>
+        private int row;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GrayscaleReader"/> class.
+        /// </summary>
+        /// <param name="useAlpha">
+        /// If set to <c>true</c> the color reader will also read the
+        /// alpha channel from the scanline.
+        /// </param>
+        public GrayscaleReader(bool useAlpha)
+        {
+            this.useAlpha = useAlpha;
+        }
+
+        /// <summary>
+        /// Reads the specified scanline.
+        /// </summary>
+        /// <param name="scanline">The scanline.</param>
+        /// <param name="pixels">The pixels, where the colors should be stored in RGBA format.</param>
+        /// <param name="header">
+        /// The header, which contains information about the png file, like
+        /// the width of the image and the height.
+        /// </param>
+        public void ReadScanline(byte[] scanline, byte[] pixels, PngHeader header)
+        {
+            int offset;
+
+            byte[] newScanline = scanline.ToArrayByBitsLength(header.BitDepth);
+
+            if (this.useAlpha)
+            {
+                for (int x = 0; x < header.Width / 2; x++)
+                {
+                    offset = ((this.row * header.Width) + x) * 4;
+
+                    pixels[offset + 0] = newScanline[x * 2];
+                    pixels[offset + 1] = newScanline[x * 2];
+                    pixels[offset + 2] = newScanline[x * 2];
+                    pixels[offset + 3] = newScanline[(x * 2) + 1];
+                }
+            }
+            else
+            {
+                for (int x = 0; x < header.Width; x++)
+                {
+                    offset = ((this.row * header.Width) + x) * 4;
+
+                    pixels[offset + 0] = newScanline[x];
+                    pixels[offset + 1] = newScanline[x];
+                    pixels[offset + 2] = newScanline[x];
+                    pixels[offset + 3] = 255;
+                }
+            }
+
+            this.row++;
+        }
+    }
+}

src/ImageProcessor/Formats/Png/IColorReader.cs

@@ -0,0 +1,31 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="IColorReader.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Encapsulates methods for color readers, which are responsible for reading
+//   different color formats from a png file.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Encapsulates methods for color readers, which are responsible for reading 
+    /// different color formats from a png file.
+    /// </summary>
+    public interface IColorReader
+    {
+        /// <summary>
+        /// Reads the specified scanline.
+        /// </summary>
+        /// <param name="scanline">The scanline.</param>
+        /// <param name="pixels">The pixels, where the colors should be stored in RGBA format.</param>
+        /// <param name="header">
+        /// The header, which contains information about the png file, like
+        /// the width of the image and the height.
+        /// </param>
+        void ReadScanline(byte[] scanline, byte[] pixels, PngHeader header);
+    }
+}

src/ImageProcessor/Formats/Png/PaletteIndexReader.cs

@@ -0,0 +1,95 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PaletteIndexReader.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   A color reader for reading palette indices from the png file.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// A color reader for reading palette indices from the png file.
+    /// </summary>
+    public sealed class PaletteIndexReader : IColorReader
+    {
+        /// <summary>
+        /// The palette.
+        /// </summary>
+        private readonly byte[] palette;
+
+        /// <summary>
+        /// The alpha palette.
+        /// </summary>
+        private readonly byte[] paletteAlpha;
+
+        /// <summary>
+        /// The current row.
+        /// </summary>
+        private int row;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PaletteIndexReader"/> class.
+        /// </summary>
+        /// <param name="palette">The palette as simple byte array. It will contains 3 values for each
+        /// color, which represents the red-, the green- and the blue channel.</param>
+        /// <param name="paletteAlpha">The alpha palette. Can be null, if the image does not have an
+        /// alpha channel and can contain less entries than the number of colors in the palette.</param>
+        public PaletteIndexReader(byte[] palette, byte[] paletteAlpha)
+        {
+            this.palette = palette;
+            this.paletteAlpha = paletteAlpha;
+        }
+
+        /// <summary>
+        /// Reads the specified scanline.
+        /// </summary>
+        /// <param name="scanline">The scanline.</param>
+        /// <param name="pixels">The pixels, where the colors should be stored in RGBA format.</param>
+        /// <param name="header">The header, which contains information about the png file, like
+        /// the width of the image and the height.</param>
+        public void ReadScanline(byte[] scanline, byte[] pixels, PngHeader header)
+        {
+            byte[] newScanline = scanline.ToArrayByBitsLength(header.BitDepth);
+            int offset, index;
+
+            if (this.paletteAlpha != null && this.paletteAlpha.Length > 0)
+            {
+                // If the alpha palette is not null and does one or
+                // more entries, this means, that the image contains and alpha
+                // channel and we should try to read it.
+                for (int i = 0; i < header.Width; i++)
+                {
+                    index = newScanline[i];
+
+                    offset = ((this.row * header.Width) + i) * 4;
+
+                    pixels[offset + 0] = this.palette[(index * 3) + 2];
+                    pixels[offset + 1] = this.palette[(index * 3) + 1];
+                    pixels[offset + 2] = this.palette[(index * 3) + 0];
+                    pixels[offset + 3] = this.paletteAlpha.Length > index
+                                                ? this.paletteAlpha[index]
+                                                : (byte)255;
+                }
+            }
+            else
+            {
+                for (int i = 0; i < header.Width; i++)
+                {
+                    index = newScanline[i];
+
+                    offset = ((this.row * header.Width) + i) * 4;
+
+                    pixels[offset + 0] = this.palette[(index * 3) + 2];
+                    pixels[offset + 1] = this.palette[(index * 3) + 1];
+                    pixels[offset + 2] = this.palette[(index * 3) + 0];
+                    pixels[offset + 3] = 255;
+                }
+            }
+
+            this.row++;
+        }
+    }
+}

src/ImageProcessor/Formats/Png/PngChunk.cs

@@ -0,0 +1,44 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngChunk.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Stores header information about a chunk.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Stores header information about a chunk.
+    /// </summary>
+    internal sealed class PngChunk
+    {
+        /// <summary>
+        /// Gets or sets the length.
+        /// An unsigned integer giving the number of bytes in the chunk's 
+        /// data field. The length counts only the data field, not itself, 
+        /// the chunk type code, or the CRC. Zero is a valid length
+        /// </summary>
+        public int Length { get; set; }
+
+        /// <summary>
+        /// Gets or sets the chunk type as string with 4 chars.
+        /// </summary>
+        public string Type { get; set; }
+
+        /// <summary>
+        /// Gets or sets the data bytes appropriate to the chunk type, if any. 
+        /// This field can be of zero length. 
+        /// </summary>
+        public byte[] Data { get; set; }
+
+        /// <summary>
+        /// Gets or sets a CRC (Cyclic Redundancy Check) calculated on the preceding bytes in the chunk, 
+        /// including the chunk type code and chunk data fields, but not including the length field. 
+        /// The CRC is always present, even for chunks containing no data
+        /// </summary>
+        public uint Crc { get; set; }
+    }
+}

src/ImageProcessor/Formats/Png/PngChunkTypes.cs

@@ -0,0 +1,67 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngChunkTypes.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Contains a list of possible chunk type identifiers.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Contains a list of possible chunk type identifiers.
+    /// </summary>
+    internal static class PngChunkTypes
+    {
+        /// <summary>
+        /// The first chunk in a png file. Can only exists once. Contains 
+        /// common information like the width and the height of the image or
+        /// the used compression method.
+        /// </summary>
+        public const string Header = "IHDR";
+
+        /// <summary>
+        /// The PLTE chunk contains from 1 to 256 palette entries, each a three byte
+        /// series in the RGB format.
+        /// </summary>
+        public const string Palette = "PLTE";
+
+        /// <summary>
+        /// The IDAT chunk contains the actual image data. The image can contains more
+        /// than one chunk of this type. All chunks together are the whole image.
+        /// </summary>
+        public const string Data = "IDAT";
+
+        /// <summary>
+        /// This chunk must appear last. It marks the end of the PNG data stream. 
+        /// The chunk's data field is empty. 
+        /// </summary>
+        public const string End = "IEND";
+
+        /// <summary>
+        /// This chunk specifies that the image uses simple transparency: 
+        /// either alpha values associated with palette entries (for indexed-color images) 
+        /// or a single transparent color (for grayscale and true color images). 
+        /// </summary>
+        public const string PaletteAlpha = "tRNS";
+
+        /// <summary>
+        /// Textual information that the encoder wishes to record with the image can be stored in 
+        /// tEXt chunks. Each tEXt chunk contains a keyword and a text string.
+        /// </summary>
+        public const string Text = "tEXt";
+
+        /// <summary>
+        /// This chunk specifies the relationship between the image samples and the desired 
+        /// display output intensity.
+        /// </summary>
+        public const string Gamma = "gAMA";
+
+        /// <summary>
+        /// The pHYs chunk specifies the intended pixel size or aspect ratio for display of the image. 
+        /// </summary>
+        public const string Physical = "pHYs";
+    }
+}

src/ImageProcessor/Formats/Png/PngColorTypeInformation.cs

@@ -0,0 +1,66 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngColorTypeInformation.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Contains information that are required when loading a png with a specific color type.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System;
+
+    /// <summary>
+    /// Contains information that are required when loading a png with a specific color type.
+    /// </summary>
+    internal sealed class PngColorTypeInformation
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PngColorTypeInformation"/> class with 
+        /// the scanline factory, the function to create the color reader and the supported bit depths.
+        /// </summary>
+        /// <param name="scanlineFactor">The scanline factor.</param>
+        /// <param name="supportedBitDepths">The supported bit depths.</param>
+        /// <param name="scanlineReaderFactory">The factory to create the color reader.</param>
+        public PngColorTypeInformation(int scanlineFactor, int[] supportedBitDepths, Func<byte[], byte[], IColorReader> scanlineReaderFactory)
+        {
+            this.ChannelsPerColor = scanlineFactor;
+            this.ScanlineReaderFactory = scanlineReaderFactory;
+            this.SupportedBitDepths = supportedBitDepths;
+        }
+
+        /// <summary>
+        /// Gets an array with the bit depths that are supported for the color type
+        /// where this object is created for.
+        /// </summary>
+        /// <value>The supported bit depths that can be used in combination with this color type.</value>
+        public int[] SupportedBitDepths { get; private set; }
+
+        /// <summary>
+        /// Gets a function that is used the create the color reader for the color type where 
+        /// this object is created for.
+        /// </summary>
+        /// <value>The factory function to create the color type.</value>
+        public Func<byte[], byte[], IColorReader> ScanlineReaderFactory { get; private set; }
+
+        /// <summary>
+        /// Gets a factor that is used when iterating through the scan lines.
+        /// </summary>
+        /// <value>The scanline factor.</value>
+        public int ChannelsPerColor { get; private set; }
+
+        /// <summary>
+        /// Creates the color reader for the color type where this object is create for.
+        /// </summary>
+        /// <param name="palette">The palette of the image. Can be null when no palette is used.</param>
+        /// <param name="paletteAlpha">The alpha palette of the image. Can be null when 
+        /// no palette is used for the image or when the image has no alpha.</param>
+        /// <returns>The color reader for the image.</returns>
+        public IColorReader CreateColorReader(byte[] palette, byte[] paletteAlpha)
+        {
+            return this.ScanlineReaderFactory(palette, paletteAlpha);
+        }
+    }
+}

src/ImageProcessor/Formats/Png/PngDecoder.cs

@@ -0,0 +1,98 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngDecoder.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Encoder for generating a image out of a png stream.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System;
+    using System.IO;
+
+    /// <summary>
+    /// Encoder for generating a image out of a png stream.
+    /// </summary>
+    /// <remarks>
+    /// At the moment the following features are supported:
+    /// <para>
+    /// <b>Filters:</b> all filters are supported.
+    /// </para>
+    /// <para>
+    /// <b>Pixel formats:</b>
+    /// <list type="bullet">
+    ///     <item>RGBA (True color) with alpha (8 bit).</item>
+    ///     <item>RGB (True color) without alpha (8 bit).</item>
+    ///     <item>Greyscale with alpha (8 bit).</item>
+    ///     <item>Greyscale without alpha (8 bit).</item>
+    ///     <item>Palette Index with alpha (8 bit).</item>
+    ///     <item>Palette Index without alpha (8 bit).</item>
+    /// </list>
+    /// </para> 
+    /// </remarks>
+    public class PngDecoder : IImageDecoder
+    {
+        /// <summary>
+        /// Gets the size of the header for this image type.
+        /// </summary>
+        /// <value>The size of the header.</value>
+        public int HeaderSize
+        {
+            get
+            {
+                return 8;
+            }
+        }
+
+        /// <summary>
+        /// Returns a value indicating whether the <see cref="IImageDecoder"/> supports the specified
+        /// file header.
+        /// </summary>
+        /// <param name="extension">The <see cref="string"/> containing the file extension.</param>
+        /// <returns>
+        /// True if the decoder supports the file extension; otherwise, false.
+        /// </returns>
+        public bool IsSupportedFileExtension(string extension)
+        {
+            Guard.NotNullOrEmpty(extension, "extension");
+
+            extension = extension.StartsWith(".") ? extension.Substring(1) : extension;
+
+            return extension.Equals("PNG", StringComparison.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// Returns a value indicating whether the <see cref="IImageDecoder"/> supports the specified
+        /// file header.
+        /// </summary>
+        /// <param name="header">The <see cref="T:byte[]"/> containing the file header.</param>
+        /// <returns>
+        /// True if the decoder supports the file header; otherwise, false.
+        /// </returns>
+        public bool IsSupportedFileFormat(byte[] header)
+        {
+            return header.Length >= 8 &&
+                   header[0] == 0x89 &&
+                   header[1] == 0x50 && // P
+                   header[2] == 0x4E && // N
+                   header[3] == 0x47 && // G
+                   header[4] == 0x0D && // CR
+                   header[5] == 0x0A && // LF
+                   header[6] == 0x1A && // EOF
+                   header[7] == 0x0A;   // LF
+        }
+
+        /// <summary>
+        /// Decodes the image from the specified stream to the <see cref="ImageBase"/>.
+        /// </summary>
+        /// <param name="image">The <see cref="ImageBase"/> to decode to.</param>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        public void Decode(Image image, Stream stream)
+        {
+            new PngDecoderCore().Decode(image, stream);
+        }
+    }
+}

src/ImageProcessor/Formats/Png/PngDecoderCore.cs

@@ -0,0 +1,554 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngDecoderCore.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Performs the png decoding operation.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System;
+    using System.Collections.Generic;
+    using System.IO;
+    using System.Linq;
+
+    using ICSharpCode.SharpZipLib.Checksums;
+    using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
+
+    /// <summary>
+    /// Performs the png decoding operation.
+    /// </summary>
+    internal class PngDecoderCore
+    {
+        /// <summary>
+        /// The maximum chunk size.
+        /// </summary>
+        private const int MaxChunkSize = 1024 * 1024;
+
+        /// <summary>
+        /// The dictionary of available color types.
+        /// </summary>
+        private static readonly Dictionary<int, PngColorTypeInformation> ColorTypes
+            = new Dictionary<int, PngColorTypeInformation>();
+
+        /// <summary>
+        /// The image to decode.
+        /// </summary>
+        private Image currentImage;
+
+        /// <summary>
+        /// The stream to decode to.
+        /// </summary>
+        private Stream currentStream;
+
+        /// <summary>
+        /// The png header.
+        /// </summary>
+        private PngHeader header;
+
+        /// <summary>
+        /// Initializes static members of the <see cref="PngDecoderCore"/> class.
+        /// </summary>
+        static PngDecoderCore()
+        {
+            ColorTypes.Add(
+                0,
+                new PngColorTypeInformation(
+                    1,
+                    new[] { 1, 2, 4, 8 },
+                    (p, a) => new GrayscaleReader(false)));
+
+            ColorTypes.Add(
+                2,
+                new PngColorTypeInformation(
+                    3,
+                    new[] { 8 },
+                    (p, a) => new TrueColorReader(false)));
+
+            ColorTypes.Add(
+                3,
+                new PngColorTypeInformation(
+                    1,
+                    new[] { 1, 2, 4, 8 },
+                    (p, a) => new PaletteIndexReader(p, a)));
+
+            ColorTypes.Add(
+                4,
+                new PngColorTypeInformation(
+                    2,
+                    new[] { 8 },
+                    (p, a) => new GrayscaleReader(true)));
+
+            ColorTypes.Add(
+                6,
+                new PngColorTypeInformation(
+                    4,
+                    new[] { 8 },
+                    (p, a) => new TrueColorReader(true)));
+        }
+
+        /// <summary>
+        /// Decodes the stream to the image.
+        /// </summary>
+        /// <param name="image">The image to decode to.</param>
+        /// <param name="stream">The stream containing image data. </param>
+        /// <exception cref="ImageFormatException">
+        /// Thrown if the stream does not contain and end chunk.
+        /// </exception>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// Thrown if the image is larger than the maximum allowable size.
+        /// </exception>
+        public void Decode(Image image, Stream stream)
+        {
+            this.currentImage = image;
+            this.currentStream = stream;
+            this.currentStream.Seek(8, SeekOrigin.Current);
+
+            bool isEndChunkReached = false;
+
+            byte[] palette = null;
+            byte[] paletteAlpha = null;
+
+            using (MemoryStream dataStream = new MemoryStream())
+            {
+                PngChunk currentChunk;
+                while ((currentChunk = this.ReadChunk()) != null)
+                {
+                    if (isEndChunkReached)
+                    {
+                        throw new ImageFormatException("Image does not end with end chunk.");
+                    }
+
+                    if (currentChunk.Type == PngChunkTypes.Header)
+                    {
+                        this.ReadHeaderChunk(currentChunk.Data);
+                        this.ValidateHeader();
+                    }
+                    else if (currentChunk.Type == PngChunkTypes.Physical)
+                    {
+                        this.ReadPhysicalChunk(currentChunk.Data);
+                    }
+                    else if (currentChunk.Type == PngChunkTypes.Data)
+                    {
+                        dataStream.Write(currentChunk.Data, 0, currentChunk.Data.Length);
+                    }
+                    else if (currentChunk.Type == PngChunkTypes.Palette)
+                    {
+                        palette = currentChunk.Data;
+                    }
+                    else if (currentChunk.Type == PngChunkTypes.PaletteAlpha)
+                    {
+                        paletteAlpha = currentChunk.Data;
+                    }
+                    else if (currentChunk.Type == PngChunkTypes.Text)
+                    {
+                        this.ReadTextChunk(currentChunk.Data);
+                    }
+                    else if (currentChunk.Type == PngChunkTypes.End)
+                    {
+                        isEndChunkReached = true;
+                    }
+                }
+
+                if (this.header.Width > ImageBase.MaxWidth || this.header.Height > ImageBase.MaxHeight)
+                {
+                    throw new ArgumentOutOfRangeException(
+                        string.Format(
+                            "The input png '{0}x{1}' is bigger then the max allowed size '{2}x{3}'",
+                            this.header.Width,
+                            this.header.Height,
+                            ImageBase.MaxWidth,
+                            ImageBase.MaxHeight));
+                }
+
+                byte[] pixels = new byte[this.header.Width * this.header.Height * 4];
+
+                PngColorTypeInformation colorTypeInformation = ColorTypes[this.header.ColorType];
+
+                if (colorTypeInformation != null)
+                {
+                    IColorReader colorReader = colorTypeInformation.CreateColorReader(palette, paletteAlpha);
+
+                    this.ReadScanlines(dataStream, pixels, colorReader, colorTypeInformation);
+                }
+
+                image.SetPixels(this.header.Width, this.header.Height, pixels);
+            }
+        }
+
+        /// <summary>
+        /// Reads the data chunk containing physical dimension data.
+        /// </summary>
+        /// <param name="data">The data containing physical data.</param>
+        private void ReadPhysicalChunk(byte[] data)
+        {
+            Array.Reverse(data, 0, 4);
+            Array.Reverse(data, 4, 4);
+
+            this.currentImage.DensityX = BitConverter.ToInt32(data, 0) / 39.3700787d;
+            this.currentImage.DensityY = BitConverter.ToInt32(data, 4) / 39.3700787d;
+        }
+
+        /// <summary>
+        /// Calculates the scanline length.
+        /// </summary>
+        /// <param name="colorTypeInformation">The color type information.</param>
+        /// <returns>The <see cref="int"/> representing the length.</returns>
+        private int CalculateScanlineLength(PngColorTypeInformation colorTypeInformation)
+        {
+            int scanlineLength = this.header.Width * this.header.BitDepth * colorTypeInformation.ChannelsPerColor;
+
+            int amount = scanlineLength % 8;
+            if (amount != 0)
+            {
+                scanlineLength += 8 - amount;
+            }
+
+            return scanlineLength / 8;
+        }
+
+        /// <summary>
+        /// Calculates a scanline step.
+        /// </summary>
+        /// <param name="colorTypeInformation">The color type information.</param>
+        /// <returns>The <see cref="int"/> representing the length of each step.</returns>
+        private int CalculateScanlineStep(PngColorTypeInformation colorTypeInformation)
+        {
+            int scanlineStep = 1;
+
+            if (this.header.BitDepth >= 8)
+            {
+                scanlineStep = (colorTypeInformation.ChannelsPerColor * this.header.BitDepth) / 8;
+            }
+
+            return scanlineStep;
+        }
+
+        /// <summary>
+        /// Reads the scanlines within the image.
+        /// </summary>
+        /// <param name="dataStream">The <see cref="MemoryStream"/> containing data.</param>
+        /// <param name="pixels">
+        /// The <see cref="T:byte[]"/> containing pixel data.</param>
+        /// <param name="colorReader">The color reader.</param>
+        /// <param name="colorTypeInformation">The color type information.</param>
+        private void ReadScanlines(MemoryStream dataStream, byte[] pixels, IColorReader colorReader, PngColorTypeInformation colorTypeInformation)
+        {
+            dataStream.Position = 0;
+
+            int scanlineLength = this.CalculateScanlineLength(colorTypeInformation);
+            int scanlineStep = this.CalculateScanlineStep(colorTypeInformation);
+
+            byte[] lastScanline = new byte[scanlineLength];
+            byte[] currentScanline = new byte[scanlineLength];
+            int filter = 0, column = -1;
+
+            using (InflaterInputStream compressedStream = new InflaterInputStream(dataStream))
+            {
+                int readByte;
+                while ((readByte = compressedStream.ReadByte()) >= 0)
+                {
+                    if (column == -1)
+                    {
+                        filter = readByte;
+
+                        column++;
+                    }
+                    else
+                    {
+                        currentScanline[column] = (byte)readByte;
+
+                        byte a;
+                        byte b;
+                        byte c;
+
+                        if (column >= scanlineStep)
+                        {
+                            a = currentScanline[column - scanlineStep];
+                            c = lastScanline[column - scanlineStep];
+                        }
+                        else
+                        {
+                            a = 0;
+                            c = 0;
+                        }
+
+                        b = lastScanline[column];
+
+                        if (filter == 1)
+                        {
+                            currentScanline[column] = (byte)(currentScanline[column] + a);
+                        }
+                        else if (filter == 2)
+                        {
+                            currentScanline[column] = (byte)(currentScanline[column] + b);
+                        }
+                        else if (filter == 3)
+                        {
+                            currentScanline[column] = (byte)(currentScanline[column] + (byte)((a + b) / 2));
+                        }
+                        else if (filter == 4)
+                        {
+                            currentScanline[column] = (byte)(currentScanline[column] + PathPredicator(a, b, c));
+                        }
+
+                        column++;
+
+                        if (column == scanlineLength)
+                        {
+                            colorReader.ReadScanline(currentScanline, pixels, this.header);
+                            column = -1;
+
+                            Utils.Swap(ref currentScanline, ref lastScanline);
+                        }
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// TODO: Document this
+        /// </summary>
+        /// <param name="a">The a.</param>
+        /// <param name="b">The b.</param>
+        /// <param name="c">The c.</param>
+        /// <returns>
+        /// The <see cref="byte"/>.
+        /// </returns>
+        private static byte PathPredicator(byte a, byte b, byte c)
+        {
+            byte predicator;
+
+            int p = a + b - c;
+            int pa = Math.Abs(p - a);
+            int pb = Math.Abs(p - b);
+            int pc = Math.Abs(p - c);
+
+            if (pa <= pb && pa <= pc)
+            {
+                predicator = a;
+            }
+            else if (pb <= pc)
+            {
+                predicator = b;
+            }
+            else
+            {
+                predicator = c;
+            }
+
+            return predicator;
+        }
+
+        /// <summary>
+        /// Reads a text chunk containing image properties from the data.
+        /// </summary>
+        /// <param name="data">The <see cref="T:byte[]"/> containing  data.</param>
+        private void ReadTextChunk(byte[] data)
+        {
+            int zeroIndex = 0;
+
+            for (int i = 0; i < data.Length; i++)
+            {
+                if (data[i] == 0)
+                {
+                    zeroIndex = i;
+                    break;
+                }
+            }
+
+            string name = System.Text.Encoding.Unicode.GetString(data, 0, zeroIndex);
+            string value = System.Text.Encoding.Unicode.GetString(data, zeroIndex + 1, data.Length - zeroIndex - 1);
+
+            this.currentImage.Properties.Add(new ImageProperty(name, value));
+        }
+
+        /// <summary>
+        /// Reads a header chunk from the data.
+        /// </summary>
+        /// <param name="data">The <see cref="T:byte[]"/> containing  data.</param>
+        private void ReadHeaderChunk(byte[] data)
+        {
+            this.header = new PngHeader();
+
+            Array.Reverse(data, 0, 4);
+            Array.Reverse(data, 4, 4);
+
+            this.header.Width = BitConverter.ToInt32(data, 0);
+            this.header.Height = BitConverter.ToInt32(data, 4);
+
+            this.header.BitDepth = data[8];
+            this.header.ColorType = data[9];
+            this.header.FilterMethod = data[11];
+            this.header.InterlaceMethod = data[12];
+            this.header.CompressionMethod = data[10];
+        }
+
+        /// <summary>
+        /// Validates the png header.
+        /// </summary>
+        /// <exception cref="ImageFormatException">
+        /// Thrown if the image does pass validation.
+        /// </exception>
+        private void ValidateHeader()
+        {
+            if (!ColorTypes.ContainsKey(this.header.ColorType))
+            {
+                throw new ImageFormatException("Color type is not supported or not valid.");
+            }
+
+            if (!ColorTypes[this.header.ColorType].SupportedBitDepths.Contains(this.header.BitDepth))
+            {
+                throw new ImageFormatException("Bit depth is not supported or not valid.");
+            }
+
+            if (this.header.FilterMethod != 0)
+            {
+                throw new ImageFormatException("The png specification only defines 0 as filter method.");
+            }
+
+            if (this.header.InterlaceMethod != 0)
+            {
+                throw new ImageFormatException("Interlacing is not supported.");
+            }
+        }
+
+        /// <summary>
+        /// Reads a chunk from the stream.
+        /// </summary>
+        /// <returns>
+        /// The <see cref="PngChunk"/>.
+        /// </returns>
+        private PngChunk ReadChunk()
+        {
+            PngChunk chunk = new PngChunk();
+
+            if (this.ReadChunkLength(chunk) == 0)
+            {
+                return null;
+            }
+
+            byte[] typeBuffer = this.ReadChunkType(chunk);
+
+            this.ReadChunkData(chunk);
+            this.ReadChunkCrc(chunk, typeBuffer);
+
+            return chunk;
+        }
+
+        /// <summary>
+        /// Reads the cycle redundancy chunk from the data.
+        /// </summary>
+        /// <param name="chunk">The chunk.</param>
+        /// <param name="typeBuffer">The type buffer.</param>
+        /// <exception cref="ImageFormatException">
+        /// Thrown if the input stream is not valid or corrupt.
+        /// </exception>
+        private void ReadChunkCrc(PngChunk chunk, byte[] typeBuffer)
+        {
+            byte[] crcBuffer = new byte[4];
+
+            int numBytes = this.currentStream.Read(crcBuffer, 0, 4);
+            if (numBytes.IsBetween(1, 3))
+            {
+                throw new ImageFormatException("Image stream is not valid!");
+            }
+
+            Array.Reverse(crcBuffer);
+
+            chunk.Crc = BitConverter.ToUInt32(crcBuffer, 0);
+
+            Crc32 crc = new Crc32();
+            crc.Update(typeBuffer);
+            crc.Update(chunk.Data);
+
+            if (crc.Value != chunk.Crc)
+            {
+                throw new ImageFormatException("CRC Error. PNG Image chunk is corrupt!");
+            }
+        }
+
+        /// <summary>
+        /// Reads the chunk data from the stream.
+        /// </summary>
+        /// <param name="chunk">The chunk.</param>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// Thrown if the chunk length exceeds the maximum allowable size.
+        /// </exception>
+        private void ReadChunkData(PngChunk chunk)
+        {
+            if (chunk.Length > MaxChunkSize)
+            {
+                throw new ArgumentOutOfRangeException(
+                    string.Format(
+                    "Png chunk size '{0}' exceeds the '{1}'",
+                    chunk.Length,
+                    MaxChunkSize));
+            }
+
+            chunk.Data = new byte[chunk.Length];
+            this.currentStream.Read(chunk.Data, 0, chunk.Length);
+        }
+
+        /// <summary>
+        /// Identifies the chunk type from the chunk.
+        /// </summary>
+        /// <param name="chunk">The chunk.</param>
+        /// <returns>
+        /// The <see cref="T:byte[]"/> containing identifying information.
+        /// </returns>
+        /// <exception cref="ImageFormatException">
+        /// Thrown if the input stream is not valid.
+        /// </exception>
+        private byte[] ReadChunkType(PngChunk chunk)
+        {
+            byte[] typeBuffer = new byte[4];
+
+            int numBytes = this.currentStream.Read(typeBuffer, 0, 4);
+            if (numBytes.IsBetween(1, 3))
+            {
+                throw new ImageFormatException("Image stream is not valid!");
+            }
+
+            char[] chars = new char[4];
+            chars[0] = (char)typeBuffer[0];
+            chars[1] = (char)typeBuffer[1];
+            chars[2] = (char)typeBuffer[2];
+            chars[3] = (char)typeBuffer[3];
+
+            chunk.Type = new string(chars);
+
+            return typeBuffer;
+        }
+
+        /// <summary>
+        /// Calculates the length of the given chunk.
+        /// </summary>
+        /// <param name="chunk">he chunk.</param>
+        /// <returns>
+        /// The <see cref="int"/> representing the chunk length.
+        /// </returns>
+        /// <exception cref="ImageFormatException">
+        /// Thrown if the input stream is not valid.
+        /// </exception>
+        private int ReadChunkLength(PngChunk chunk)
+        {
+            byte[] lengthBuffer = new byte[4];
+
+            int numBytes = this.currentStream.Read(lengthBuffer, 0, 4);
+            if (numBytes.IsBetween(1, 3))
+            {
+                throw new ImageFormatException("Image stream is not valid!");
+            }
+
+            Array.Reverse(lengthBuffer);
+
+            chunk.Length = BitConverter.ToInt32(lengthBuffer, 0);
+
+            return numBytes;
+        }
+    }
+}

src/ImageProcessor/Formats/Png/PngEncoder.cs

@@ -0,0 +1,488 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngEncoder.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Image encoder for writing image data to a stream in png format.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    using System;
+    using System.IO;
+
+    using ICSharpCode.SharpZipLib.Checksums;
+    using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
+
+    /// <summary>
+    /// Image encoder for writing image data to a stream in png format.
+    /// </summary>
+    public class PngEncoder : IImageEncoder
+    {
+        /// <summary>
+        /// The maximum block size.
+        /// </summary>
+        private const int MaxBlockSize = 0xFFFF;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PngEncoder"/> class.
+        /// </summary>
+        public PngEncoder()
+        {
+            this.Gamma = 2.2f;
+        }
+
+        /// <summary>
+        /// Gets or sets the quality of output for images.
+        /// </summary>
+        /// <remarks>Png is a lossless format so this is not used in this encoder.</remarks>
+        public int Quality { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether this encoder
+        /// will write the image uncompressed the stream.
+        /// </summary>
+        /// <value>
+        /// <c>true</c> if the image should be written uncompressed to
+        /// the stream; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsWritingUncompressed { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether this instance is writing
+        /// gamma information to the stream. The default value is false.
+        /// </summary>
+        /// <value>
+        /// <c>true</c> if this instance is writing gamma 
+        /// information to the stream.; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsWritingGamma { get; set; }
+
+        /// <summary>
+        /// Gets or sets the gamma value, that will be written
+        /// the the stream, when the <see cref="IsWritingGamma"/> property
+        /// is set to true. The default value is 2.2f.
+        /// </summary>
+        /// <value>The gamma value of the image.</value>
+        public double Gamma { get; set; }
+
+        /// <summary>
+        /// Gets the default file extension for this encoder.
+        /// </summary>
+        /// <value>The default file extension for this encoder.</value>
+        public string Extension
+        {
+            get { return "PNG"; }
+        }
+
+        /// <summary>
+        /// Indicates if the image encoder supports the specified
+        /// file extension.
+        /// </summary>
+        /// <param name="extension">The file extension.</param>
+        /// <returns><c>true</c>, if the encoder supports the specified
+        /// extensions; otherwise <c>false</c>.
+        /// </returns>
+        /// <exception cref="ArgumentNullException"><paramref name="extension"/>
+        /// is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="ArgumentException"><paramref name="extension"/> is a string
+        /// of length zero or contains only blanks.</exception>
+        public bool IsSupportedFileExtension(string extension)
+        {
+            Guard.NotNullOrEmpty(extension, "extension");
+
+            extension = extension.StartsWith(".") ? extension.Substring(1) : extension;
+
+            return extension.Equals("PNG", StringComparison.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// Encodes the data of the specified image and writes the result to
+        /// the specified stream.
+        /// </summary>
+        /// <param name="image">The image, where the data should be get from.
+        /// Cannot be null (Nothing in Visual Basic).</param>
+        /// <param name="stream">The stream, where the image data should be written to.
+        /// Cannot be null (Nothing in Visual Basic).</param>
+        /// <exception cref="ArgumentNullException">
+        /// <para><paramref name="image"/> is null (Nothing in Visual Basic).</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="stream"/> is null (Nothing in Visual Basic).</para>
+        /// </exception>
+        public void Encode(ImageBase image, Stream stream)
+        {
+            Guard.NotNull(image, "image");
+            Guard.NotNull(stream, "stream");
+
+            // Write the png header.
+            stream.Write(
+                new byte[]
+                    { 
+                    0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A
+                    },
+                0,
+                8);
+
+            PngHeader header = new PngHeader
+            {
+                Width = image.Width,
+                Height = image.Height,
+                ColorType = 6,
+                BitDepth = 8,
+                FilterMethod = 0,
+                CompressionMethod = 0,
+                InterlaceMethod = 0
+            };
+
+            this.WriteHeaderChunk(stream, header);
+            this.WritePhysicalChunk(stream, image);
+            this.WriteGammaChunk(stream);
+
+            if (this.IsWritingUncompressed)
+            {
+                this.WriteDataChunksFast(stream, image);
+            }
+            else
+            {
+                this.WriteDataChunks(stream, image);
+            }
+
+            this.WriteEndChunk(stream);
+            stream.Flush();
+        }
+
+        /// <summary>
+        /// Writes an integer to the byte array.
+        /// </summary>
+        /// <param name="data">The <see cref="T:byte[]"/> containing image data.</param>
+        /// <param name="offset">The amount to offset by.</param>
+        /// <param name="value">The value to write.</param>
+        private static void WriteInteger(byte[] data, int offset, int value)
+        {
+            byte[] buffer = BitConverter.GetBytes(value);
+
+            Array.Reverse(buffer);
+            Array.Copy(buffer, 0, data, offset, 4);
+        }
+
+        /// <summary>
+        /// Writes an integer to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="value">The value to write.</param>
+        private static void WriteInteger(Stream stream, int value)
+        {
+            byte[] buffer = BitConverter.GetBytes(value);
+
+            Array.Reverse(buffer);
+
+            stream.Write(buffer, 0, 4);
+        }
+
+        /// <summary>
+        /// Writes an unsigned integer to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="value">The value to write.</param>
+        private static void WriteInteger(Stream stream, uint value)
+        {
+            byte[] buffer = BitConverter.GetBytes(value);
+
+            Array.Reverse(buffer);
+
+            stream.Write(buffer, 0, 4);
+        }
+
+        /// <summary>
+        /// Writes the physical dimension information to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="imageBase">The image base.</param>
+        private void WritePhysicalChunk(Stream stream, ImageBase imageBase)
+        {
+            Image image = imageBase as Image;
+            if (image != null && image.DensityX > 0 && image.DensityY > 0)
+            {
+                int dpmX = (int)Math.Round(image.DensityX * 39.3700787d);
+                int dpmY = (int)Math.Round(image.DensityY * 39.3700787d);
+
+                byte[] chunkData = new byte[9];
+
+                WriteInteger(chunkData, 0, dpmX);
+                WriteInteger(chunkData, 4, dpmY);
+
+                chunkData[8] = 1;
+
+                this.WriteChunk(stream, PngChunkTypes.Physical, chunkData);
+            }
+        }
+
+        /// <summary>
+        /// Writes the gamma information to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        private void WriteGammaChunk(Stream stream)
+        {
+            if (this.IsWritingGamma)
+            {
+                int gammaValue = (int)(this.Gamma * 100000f);
+
+                byte[] fourByteData = new byte[4];
+
+                byte[] size = BitConverter.GetBytes(gammaValue);
+
+                fourByteData[0] = size[3];
+                fourByteData[1] = size[2];
+                fourByteData[2] = size[1];
+                fourByteData[3] = size[0];
+
+                this.WriteChunk(stream, PngChunkTypes.Gamma, fourByteData);
+            }
+        }
+
+        /// <summary>
+        /// Writes the pixel information to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="imageBase">The image base.</param>
+        private void WriteDataChunksFast(Stream stream, ImageBase imageBase)
+        {
+            byte[] pixels = imageBase.Pixels;
+
+            // Convert the pixel array to a new array for adding
+            // the filter byte.
+            byte[] data = new byte[(imageBase.Width * imageBase.Height * 4) + imageBase.Height];
+
+            int rowLength = (imageBase.Width * 4) + 1;
+
+            for (int y = 0; y < imageBase.Height; y++)
+            {
+                data[y * rowLength] = 0;
+                Array.Copy(pixels, y * imageBase.Width * 4, data, (y * rowLength) + 1, imageBase.Width * 4);
+            }
+
+            Adler32 adler32 = new Adler32();
+            adler32.Update(data);
+
+            using (MemoryStream tempStream = new MemoryStream())
+            {
+                int remainder = data.Length;
+
+                int blockCount;
+                if ((data.Length % MaxBlockSize) == 0)
+                {
+                    blockCount = data.Length / MaxBlockSize;
+                }
+                else
+                {
+                    blockCount = (data.Length / MaxBlockSize) + 1;
+                }
+
+                // Write headers
+                tempStream.WriteByte(0x78);
+                tempStream.WriteByte(0xDA);
+
+                for (int i = 0; i < blockCount; i++)
+                {
+                    // Write the length
+                    ushort length = (ushort)((remainder < MaxBlockSize) ? remainder : MaxBlockSize);
+
+                    tempStream.WriteByte(length == remainder ? (byte)0x01 : (byte)0x00);
+
+                    tempStream.Write(BitConverter.GetBytes(length), 0, 2);
+
+                    // Write one's compliment of length
+                    tempStream.Write(BitConverter.GetBytes((ushort)~length), 0, 2);
+
+                    // Write blocks
+                    tempStream.Write(data, i * MaxBlockSize, length);
+
+                    // Next block
+                    remainder -= MaxBlockSize;
+                }
+
+                WriteInteger(tempStream, (int)adler32.Value);
+
+                tempStream.Seek(0, SeekOrigin.Begin);
+
+                byte[] zipData = new byte[tempStream.Length];
+                tempStream.Read(zipData, 0, (int)tempStream.Length);
+
+                this.WriteChunk(stream, PngChunkTypes.Data, zipData);
+            }
+        }
+
+        /// <summary>
+        /// Writes the pixel information to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="imageBase">The image base.</param>
+        private void WriteDataChunks(Stream stream, ImageBase imageBase)
+        {
+            byte[] pixels = imageBase.Pixels;
+
+            byte[] data = new byte[(imageBase.Width * imageBase.Height * 4) + imageBase.Height];
+
+            int rowLength = (imageBase.Width * 4) + 1;
+
+            for (int y = 0; y < imageBase.Height; y++)
+            {
+                byte compression = 0;
+                if (y > 0)
+                {
+                    compression = 2;
+                }
+
+                data[y * rowLength] = compression;
+
+                for (int x = 0; x < imageBase.Width; x++)
+                {
+                    // Calculate the offset for the new array.
+                    int dataOffset = (y * rowLength) + (x * 4) + 1;
+
+                    // Calculate the offset for the original pixel array.
+                    int pixelOffset = ((y * imageBase.Width) + x) * 4;
+
+                    data[dataOffset + 0] = pixels[pixelOffset + 2];
+                    data[dataOffset + 1] = pixels[pixelOffset + 1];
+                    data[dataOffset + 2] = pixels[pixelOffset + 0];
+                    data[dataOffset + 3] = pixels[pixelOffset + 3];
+
+                    if (y > 0)
+                    {
+                        int lastOffset = (((y - 1) * imageBase.Width) + x) * 4;
+
+                        data[dataOffset + 0] -= pixels[lastOffset + 2];
+                        data[dataOffset + 1] -= pixels[lastOffset + 1];
+                        data[dataOffset + 2] -= pixels[lastOffset + 0];
+                        data[dataOffset + 3] -= pixels[lastOffset + 3];
+                    }
+                }
+            }
+
+            byte[] buffer;
+            int bufferLength;
+
+            MemoryStream memoryStream = null;
+            try
+            {
+                memoryStream = new MemoryStream();
+
+                using (DeflaterOutputStream outputStream = new DeflaterOutputStream(memoryStream))
+                {
+                    outputStream.Write(data, 0, data.Length);
+                    outputStream.Flush();
+                    outputStream.Finish();
+
+                    bufferLength = (int)memoryStream.Length;
+                    buffer = memoryStream.ToArray();
+                }
+            }
+            finally
+            {
+                if (memoryStream != null)
+                {
+                    memoryStream.Dispose();
+                }
+            }
+
+            int numChunks = bufferLength / MaxBlockSize;
+
+            if (bufferLength % MaxBlockSize != 0)
+            {
+                numChunks++;
+            }
+
+            for (int i = 0; i < numChunks; i++)
+            {
+                int length = bufferLength - (i * MaxBlockSize);
+
+                if (length > MaxBlockSize)
+                {
+                    length = MaxBlockSize;
+                }
+
+                this.WriteChunk(stream, PngChunkTypes.Data, buffer, i * MaxBlockSize, length);
+            }
+        }
+
+        /// <summary>
+        /// Writes the chunk end to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        private void WriteEndChunk(Stream stream)
+        {
+            this.WriteChunk(stream, PngChunkTypes.End, null);
+        }
+
+        /// <summary>
+        /// Writes the header chunk to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="header">The <see cref="PngHeader"/>.</param>
+        private void WriteHeaderChunk(Stream stream, PngHeader header)
+        {
+            byte[] chunkData = new byte[13];
+
+            WriteInteger(chunkData, 0, header.Width);
+            WriteInteger(chunkData, 4, header.Height);
+
+            chunkData[8] = header.BitDepth;
+            chunkData[9] = header.ColorType;
+            chunkData[10] = header.CompressionMethod;
+            chunkData[11] = header.FilterMethod;
+            chunkData[12] = header.InterlaceMethod;
+
+            this.WriteChunk(stream, PngChunkTypes.Header, chunkData);
+        }
+
+        /// <summary>
+        /// Writes a chunk to the stream.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> to write to.</param>
+        /// <param name="type">The type of chunk to write.</param>
+        /// <param name="data">The <see cref="T:byte[]"/> containing data.</param>
+        private void WriteChunk(Stream stream, string type, byte[] data)
+        {
+            this.WriteChunk(stream, type, data, 0, data != null ? data.Length : 0);
+        }
+
+        /// <summary>
+        /// Writes a chunk  of a specified length to the stream at the given offset.
+        /// </summary>
+        /// <param name="stream">The <see cref="Stream"/> to write to.</param>
+        /// <param name="type">The type of chunk to write.</param>
+        /// <param name="data">The <see cref="T:byte[]"/> containing data.</param>
+        /// <param name="offset">The position to offset the data at.</param>
+        /// <param name="length">The of the data to write.</param>
+        private void WriteChunk(Stream stream, string type, byte[] data, int offset, int length)
+        {
+            WriteInteger(stream, length);
+
+            byte[] typeArray = new byte[4];
+            typeArray[0] = (byte)type[0];
+            typeArray[1] = (byte)type[1];
+            typeArray[2] = (byte)type[2];
+            typeArray[3] = (byte)type[3];
+
+            stream.Write(typeArray, 0, 4);
+
+            if (data != null)
+            {
+                stream.Write(data, offset, length);
+            }
+
+            Crc32 crc32 = new Crc32();
+            crc32.Update(typeArray);
+
+            if (data != null)
+            {
+                crc32.Update(data, offset, length);
+            }
+
+            WriteInteger(stream, (uint)crc32.Value);
+        }
+    }
+}

src/ImageProcessor/Formats/Png/PngHeader.cs

@@ -0,0 +1,67 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="PngHeader.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Represents the png header chunk.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Represents the png header chunk.
+    /// </summary>
+    public sealed class PngHeader
+    {
+        /// <summary>
+        /// Gets or sets the dimension in x-direction of the image in pixels.
+        /// </summary>
+        public int Width { get; set; }
+
+        /// <summary>
+        /// Gets or sets the dimension in y-direction of the image in pixels.
+        /// </summary>
+        public int Height { get; set; }
+
+        /// <summary>
+        /// Gets or sets the bit depth.
+        /// Bit depth is a single-byte integer giving the number of bits per sample 
+        /// or per palette index (not per pixel). Valid values are 1, 2, 4, 8, and 16, 
+        /// although not all values are allowed for all color types. 
+        /// </summary>
+        public byte BitDepth { get; set; }
+
+        /// <summary>
+        /// Gets or sets the color type.
+        /// Color type is a integer that describes the interpretation of the 
+        /// image data. Color type codes represent sums of the following values: 
+        /// 1 (palette used), 2 (color used), and 4 (alpha channel used).
+        /// </summary>
+        public byte ColorType { get; set; }
+
+        /// <summary>
+        /// Gets or sets the compression method.
+        /// Indicates the method used to compress the image data. At present, 
+        /// only compression method 0 (deflate/inflate compression with a sliding 
+        /// window of at most 32768 bytes) is defined.
+        /// </summary>
+        public byte CompressionMethod { get; set; }
+
+        /// <summary>
+        /// Gets or sets the preprocessing method.
+        /// Indicates the preprocessing method applied to the image 
+        /// data before compression. At present, only filter method 0 
+        /// (adaptive filtering with five basic filter types) is defined.
+        /// </summary>
+        public byte FilterMethod { get; set; }
+
+        /// <summary>
+        /// Gets or sets the  transmission order.
+        /// Indicates the transmission order of the image data. 
+        /// Two values are currently defined: 0 (no interlace) or 1 (Adam7 interlace).
+        /// </summary>
+        public byte InterlaceMethod { get; set; }
+    }
+}

src/ImageProcessor/Formats/Png/TrueColorReader.cs

@@ -0,0 +1,81 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="TrueColorReader.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Color reader for reading true colors from a png file. Only colors
+//   with 24 or 32 bit (3 or 4 bytes) per pixel are supported at the moment.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Formats
+{
+    /// <summary>
+    /// Color reader for reading true colors from a png file. Only colors
+    /// with 24 or 32 bit (3 or 4 bytes) per pixel are supported at the moment.
+    /// </summary>
+    public sealed class TrueColorReader : IColorReader
+    {
+        /// <summary>
+        /// Whether t also read the alpha channel.
+        /// </summary>
+        private readonly bool useAlpha;
+
+        /// <summary>
+        /// The current row.
+        /// </summary>
+        private int row;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TrueColorReader"/> class.
+        /// </summary>
+        /// <param name="useAlpha">if set to <c>true</c> the color reader will also read the
+        /// alpha channel from the scanline.</param>
+        public TrueColorReader(bool useAlpha)
+        {
+            this.useAlpha = useAlpha;
+        }
+
+        /// <summary>
+        /// Reads the specified scanline.
+        /// </summary>
+        /// <param name="scanline">The scanline.</param>
+        /// <param name="pixels">The pixels, where the colors should be stored in RGBA format.</param>
+        /// <param name="header">The header, which contains information about the png file, like
+        /// the width of the image and the height.</param>
+        public void ReadScanline(byte[] scanline, byte[] pixels, PngHeader header)
+        {
+            int offset;
+
+            byte[] newScanline = scanline.ToArrayByBitsLength(header.BitDepth);
+
+            if (this.useAlpha)
+            {
+                for (int x = 0; x < newScanline.Length; x += 4)
+                {
+                    offset = ((this.row * header.Width) + (x >> 2)) * 4;
+
+                    pixels[offset + 0] = newScanline[x + 2];
+                    pixels[offset + 1] = newScanline[x + 1];
+                    pixels[offset + 2] = newScanline[x + 0];
+                    pixels[offset + 3] = newScanline[x + 3];
+                }
+            }
+            else
+            {
+                for (int x = 0; x < newScanline.Length / 3; x++)
+                {
+                    offset = ((this.row * header.Width) + x) * 4;
+
+                    pixels[offset + 0] = newScanline[(x * 3) + 2];
+                    pixels[offset + 1] = newScanline[(x * 3) + 1];
+                    pixels[offset + 2] = newScanline[(x * 3) + 0];
+                    pixels[offset + 3] = 255;
+                }
+            }
+
+            this.row++;
+        }
+    }
+}

src/ImageProcessor/IImageBase.cs

@@ -1,78 +0,0 @@
-// --------------------------------------------------------------------------------------------------------------------
-// <copyright file="IImageBase.cs" company="James South">
-//   Copyright © James South and contributors.
-//   Licensed under the Apache License, Version 2.0.
-// </copyright>
-// <summary>
-//   Encapsulates all the basic properties and methods required to manipulate images.
-// </summary>
-// --------------------------------------------------------------------------------------------------------------------
-
-namespace ImageProcessor
-{
-    /// <summary>
-    /// Encapsulates all the basic properties and methods required to manipulate images.
-    /// </summary>
-    public interface IImageBase
-    {
-        /// <summary>
-        /// Gets the image pixels as byte array.
-        /// </summary>
-        /// <remarks>
-        /// The returned array has a length of Width * Height * 4 bytes
-        /// and stores the blue, the green, the red and the alpha value for
-        /// each pixel in this order.
-        /// </remarks>
-        byte[] Pixels { get; }
-
-        /// <summary>
-        /// Gets the width in pixels.
-        /// </summary>
-        int Width { get; }
-
-        /// <summary>
-        /// Gets the height in pixels.
-        /// </summary>
-        int Height { get; }
-
-        /// <summary>
-        /// Gets the pixel ratio made up of the width and height.
-        /// </summary>
-        double PixelRatio { get; }
-
-        /// <summary>
-        /// Gets the <see cref="Rectangle"/> representing the bounds of the image.
-        /// </summary>
-        Rectangle Bounds { get; }
-
-        /// <summary>
-        /// Gets or sets the color of a pixel at the specified position.
-        /// </summary>
-        /// <param name="x">
-        /// The x-coordinate of the pixel. Must be greater
-        /// than zero and smaller than the width of the pixel.
-        /// </param>
-        /// <param name="y">
-        /// The y-coordinate of the pixel. Must be greater
-        /// than zero and smaller than the width of the pixel.
-        /// </param>
-        /// <returns>The <see cref="Color"/> at the specified position.</returns>
-        Color this[int x, int y]
-        {
-            get;
-            set;
-        }
-
-        /// <summary>
-        /// Sets the pixel array of the image.
-        /// </summary>
-        /// <param name="width">
-        /// The new width of the image. Must be greater than zero.</param>
-        /// <param name="height">The new height of the image. Must be greater than zero.</param>
-        /// <param name="pixels">
-        /// The array with colors. Must be a multiple
-        /// of four, width and height.
-        /// </param>
-        void SetPixels(int width, int height, byte[] pixels);
-    }
-}

src/ImageProcessor/Image.cs

@@ -0,0 +1,299 @@
+namespace ImageProcessor
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics;
+    using System.IO;
+    using System.Linq;
+    using System.Text;
+
+    using ImageProcessor.Formats;
+
+    /// <summary>
+    /// Image class with stores the pixels and provides common functionality
+    /// such as loading images from files and streams or operation like resizing or cutting.
+    /// </summary>
+    /// <remarks>The image data is alway stored in RGBA format, where the red, the blue, the
+    /// alpha values are simple bytes.</remarks>
+    [DebuggerDisplay("Image: {PixelWidth}x{PixelHeight}")]
+    public class Image : ImageBase
+    {
+        #region Constants
+
+        /// <summary>
+        /// The default density value (dots per inch) in x direction. The default value is 75 dots per inch.
+        /// </summary>
+        public const double DefaultDensityX = 75;
+        /// <summary>
+        /// The default density value (dots per inch) in y direction. The default value is 75 dots per inch.
+        /// </summary>
+        public const double DefaultDensityY = 75;
+
+        private static readonly Lazy<List<IImageDecoder>> defaultDecoders = new Lazy<List<IImageDecoder>>(() => new List<IImageDecoder>
+        {
+            //new BmpDecoder(),
+            //new JpegDecoder(),
+            //new PngDecoder(),
+            new GifDecoder(),
+        });
+
+        private static readonly Lazy<List<IImageEncoder>> defaultEncoders = new Lazy<List<IImageEncoder>>(() => new List<IImageEncoder>
+        {
+            //new BmpEncoder(),
+            //new JpegEncoder(),
+            //new PngEncoder(),
+        });
+
+        /// <summary>
+        /// Gets a list of default decoders.
+        /// </summary>
+        public static IList<IImageDecoder> Decoders
+        {
+            get { return defaultDecoders.Value; }
+        }
+
+        /// <summary>
+        /// Gets a list of default encoders.
+        /// </summary>
+        public static IList<IImageEncoder> Encoders
+        {
+            get { return defaultEncoders.Value; }
+        }
+
+        #endregion
+
+        #region Fields
+
+        private readonly object _lockObject = new object();
+
+        #endregion
+
+        /// <summary>
+        /// If not 0, this field specifies the number of hundredths (1/100) of a second to 
+        /// wait before continuing with the processing of the Data Stream. 
+        /// The clock starts ticking immediately after the graphic is rendered. 
+        /// This field may be used in conjunction with the User Input Flag field. 
+        /// </summary>
+        public int? DelayTime { get; set; }
+
+        #region Properties
+
+        /// <summary>
+        /// Gets or sets the resolution of the image in x direction. It is defined as 
+        /// number of dots per inch and should be an positive value.
+        /// </summary>
+        /// <value>The density of the image in x direction.</value>
+        public double DensityX { get; set; }
+
+        /// <summary>
+        /// Gets or sets the resolution of the image in y direction. It is defined as 
+        /// number of dots per inch and should be an positive value.
+        /// </summary>
+        /// <value>The density of the image in y direction.</value>
+        public double DensityY { get; set; }
+
+        /// <summary>
+        /// Gets the width of the image in inches. It is calculated as the width of the image 
+        /// in pixels multiplied with the density. When the density is equals or less than zero 
+        /// the default value is used.
+        /// </summary>
+        /// <value>The width of the image in inches.</value>
+        public double InchWidth
+        {
+            get
+            {
+                double densityX = DensityX;
+
+                if (densityX <= 0)
+                {
+                    densityX = DefaultDensityX;
+                }
+
+                return Width / densityX;
+            }
+        }
+
+        /// <summary>
+        /// Gets the height of the image in inches. It is calculated as the height of the image 
+        /// in pixels multiplied with the density. When the density is equals or less than zero 
+        /// the default value is used.
+        /// </summary>
+        /// <value>The height of the image in inches.</value>
+        public double InchHeight
+        {
+            get
+            {
+                double densityY = DensityY;
+
+                if (densityY <= 0)
+                {
+                    densityY = DefaultDensityY;
+                }
+
+                return Height / densityY;
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether this image is animated.
+        /// </summary>
+        /// <value>
+        /// <c>true</c> if this image is animated; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsAnimated
+        {
+            get { return _frames.Count > 0; }
+        }
+
+        private IList<ImageFrame> _frames = new List<ImageFrame>();
+        /// <summary>
+        /// Get the other frames for the animation.
+        /// </summary>
+        /// <value>The list of frame images.</value>
+        public IList<ImageFrame> Frames
+        {
+            get { return _frames; }
+        }
+
+        private IList<ImageProperty> _properties = new List<ImageProperty>();
+        /// <summary>
+        /// Gets the list of properties for storing meta information about this image.
+        /// </summary>
+        /// <value>A list of image properties.</value>
+        public IList<ImageProperty> Properties
+        {
+            get { return _properties; }
+        }
+
+        #endregion
+
+        #region Constructors
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image"/> class
+        /// with the height and the width of the image.
+        /// </summary>
+        /// <param name="width">The width of the image in pixels.</param>
+        /// <param name="height">The height of the image in pixels.</param>
+        public Image(int width, int height)
+            : base(width, height)
+        {
+            DensityX = DefaultDensityX;
+            DensityY = DefaultDensityY;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image"/> class
+        /// by making a copy from another image.
+        /// </summary>
+        /// <param name="other">The other image, where the clone should be made from.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="other"/> is null
+        /// (Nothing in Visual Basic).</exception>
+        public Image(Image other)
+            : base(other)
+        {
+            if (other == null) throw new ArgumentNullException("Other image cannot be null.");
+
+            foreach (ImageFrame frame in other.Frames)
+            {
+                if (frame != null)
+                {
+                    Frames.Add(new ImageFrame(frame));
+                }
+            }
+
+            DensityX = DefaultDensityX;
+            DensityY = DefaultDensityY;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image"/> class.
+        /// </summary>
+        public Image()
+        {
+            DensityX = DefaultDensityX;
+            DensityY = DefaultDensityY;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image"/> class.
+        /// </summary>
+        public Image(Stream stream)
+        {
+            if (stream == null)
+            {
+                throw new ArgumentNullException("stream");
+            }
+
+            Load(stream, Decoders);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Image"/> class.
+        /// </summary>
+        public Image(Stream stream, params IImageDecoder[] decoders)
+        {
+            if (stream == null)
+            {
+                throw new ArgumentNullException("stream");
+            }
+
+            Load(stream, decoders);
+        }
+
+        #endregion Constructors
+
+        #region Methods
+
+        private void Load(Stream stream, IList<IImageDecoder> decoders)
+        {
+            try
+            {
+                if (!stream.CanRead)
+                {
+                    throw new NotSupportedException("Cannot read from the stream.");
+                }
+
+                if (!stream.CanSeek)
+                {
+                    throw new NotSupportedException("The stream does not support seeking.");
+                }
+
+                if (decoders.Count > 0)
+                {
+                    int maxHeaderSize = decoders.Max(x => x.HeaderSize);
+                    if (maxHeaderSize > 0)
+                    {
+                        byte[] header = new byte[maxHeaderSize];
+
+                        stream.Read(header, 0, maxHeaderSize);
+                        stream.Position = 0;
+
+                        var decoder = decoders.FirstOrDefault(x => x.IsSupportedFileFormat(header));
+                        if (decoder != null)
+                        {
+                            decoder.Decode(this, stream);
+                            return;
+                        }
+                    }
+                }
+
+                StringBuilder stringBuilder = new StringBuilder();
+                stringBuilder.AppendLine("Image cannot be loaded. Available decoders:");
+
+                foreach (IImageDecoder decoder in decoders)
+                {
+                    stringBuilder.AppendLine("-" + decoder);
+                }
+
+                throw new NotSupportedException(stringBuilder.ToString());
+            }
+            finally
+            {
+                stream.Dispose();
+            }
+        }
+
+        #endregion Methods
+    }
+}

src/ImageProcessor/ImageBase.cs

@@ -14,11 +14,28 @@ namespace ImageProcessor
     using System;
 
     /// <summary>
-    /// The base class of all images. Encapsulates all the properties and methods 
+    /// The base class of all images. Encapsulates the basic properties and methods 
     /// required to manipulate images.
     /// </summary>
-    public abstract class ImageBase : IImageBase
+    public abstract class ImageBase 
     {
+        /// <summary>
+        /// The maximum allowable width in pixels.
+        /// </summary>
+        private static int maxWidth = int.MaxValue;
+
+        /// <summary>
+        /// The maximum allowable height in pixels.
+        /// </summary>
+        private static int maxHeight = int.MaxValue;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImageBase"/> class.
+        /// </summary>
+        protected ImageBase()
+        {
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ImageBase"/> class.
         /// </summary>
@@ -73,6 +90,38 @@ namespace ImageProcessor
             Array.Copy(pixels, this.Pixels, pixels.Length);
         }
 
+        /// <summary>
+        /// Gets or sets the maximum allowable width in pixels.
+        /// </summary>
+        public static int MaxWidth
+        {
+            get
+            {
+                return maxWidth;
+            }
+
+            set
+            {
+                maxWidth = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the maximum allowable height in pixels.
+        /// </summary>
+        public static int MaxHeight
+        {
+            get
+            {
+                return maxHeight;
+            }
+
+            set
+            {
+                maxHeight = value;
+            }
+        }
+
         /// <summary>
         /// Gets the image pixels as byte array.
         /// </summary>

src/ImageProcessor/ImageFrame.cs

@@ -0,0 +1,41 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="ImageFrame.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Represents a single frame in a animation.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor
+{
+    using System;
+
+    /// <summary>
+    /// Represents a single frame in a animation.
+    /// </summary>
+    public class ImageFrame : ImageBase
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImageFrame"/> class.
+        /// </summary>
+        public ImageFrame()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImageFrame"/> class.
+        /// </summary>
+        /// <param name="other">
+        /// The other <see cref="ImageBase"/> to create this instance from.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        /// Thrown if the given <see cref="ImageFrame"/> is null.
+        /// </exception>
+        public ImageFrame(ImageFrame other)
+            : base(other)
+        {
+        }
+    }
+}

src/ImageProcessor/ImageProcessor.csproj

@@ -35,21 +35,52 @@
   </PropertyGroup>
   <ItemGroup>
     <!-- A reference to the entire .NET Framework is automatically included -->
-    <Folder Include="Common\Extensions\" />
-    <Folder Include="Common\Helpers\" />
-    <Folder Include="Encoders\" />
     <Folder Include="Filters\" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Common\Extensions\ByteExtensions.cs" />
+    <Compile Include="Common\Extensions\ComparableExtensions.cs" />
+    <Compile Include="Common\Helpers\Utils.cs" />
+    <Compile Include="Formats\Png\PngDecoder.cs" />
+    <Compile Include="Formats\Png\PngDecoderCore.cs" />
+    <Compile Include="Formats\Png\PngEncoder.cs" />
+    <Compile Include="Formats\Png\PngColorTypeInformation.cs" />
+    <Compile Include="Formats\Png\PngChunk.cs" />
+    <Compile Include="Formats\Png\PngChunkTypes.cs" />
+    <Compile Include="Formats\Png\TrueColorReader.cs" />
+    <Compile Include="Formats\Png\PaletteIndexReader.cs" />
+    <Compile Include="Formats\Png\GrayscaleReader.cs" />
+    <Compile Include="Formats\Png\IColorReader.cs" />
+    <Compile Include="Formats\Png\PngHeader.cs" />
+    <Compile Include="ImageProperty.cs" />
+    <Compile Include="ImageFrame.cs" />
     <Compile Include="Colors\Color.cs" />
     <Compile Include="Common\Exceptions\ImageFormatException.cs" />
-    <Compile Include="IImageBase.cs" />
+    <Compile Include="Common\Helpers\Guard.cs" />
+    <Compile Include="Formats\Gif\GifDecoder.cs" />
+    <Compile Include="Formats\Gif\LzwDecoder.cs" />
+    <Compile Include="Formats\Gif\GifLogicalScreenDescriptor.cs" />
+    <Compile Include="Formats\Gif\GifImageDescriptor.cs" />
+    <Compile Include="Formats\Gif\GifGraphicsControlExtension.cs" />
+    <Compile Include="Formats\Gif\DisposalMethod.cs" />
+    <Compile Include="Formats\IImageDecoder.cs" />
+    <Compile Include="Formats\IImageEncoder.cs" />
+    <Compile Include="Image.cs" />
     <Compile Include="ImageBase.cs" />
     <Compile Include="Numerics\Point.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Numerics\Rectangle.cs" />
     <Compile Include="Numerics\Size.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <Reference Include="ICSharpCode.SharpZipLib.Portable, Version=0.86.0.51802, Culture=neutral, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\SharpZipLib.Portable.0.86.0.0002\lib\portable-net45+netcore45+wp8+win8+wpa81+MonoTouch+MonoAndroid\ICSharpCode.SharpZipLib.Portable.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+  </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

src/ImageProcessor/ImageProcessor.csproj.DotSettings

@@ -4,4 +4,7 @@
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=common_005Cexceptions/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=common_005Cextensions/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=common_005Chelpers/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=encoders_005Cgif/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=formats_005Cgif/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=formats_005Cpng/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=numerics/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

src/ImageProcessor/ImageProperty.cs

@@ -0,0 +1,167 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="ImageProperty.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Stores meta information about a image, like the name of the author,
+//   the copyright information, the date, where the image was created
+//   or some other information.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor
+{
+    using System;
+
+    /// <summary>
+    /// Stores meta information about a image, like the name of the author,
+    /// the copyright information, the date, where the image was created
+    /// or some other information.
+    /// </summary>
+    public struct ImageProperty : IEquatable<ImageProperty>
+    {
+        /// <summary>
+        /// The name of this <see cref="ImageProperty"/> indicating which kind of 
+        /// information this property stores.
+        /// </summary>
+        /// <example>
+        /// Typical properties are the author, copyright
+        /// information or other meta information.
+        /// </example>
+        public string Name;
+
+        /// <summary>
+        /// The value of this <see cref="ImageProperty"/>.
+        /// </summary>
+        public string Value;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ImageProperty"/> struct.
+        /// </summary>
+        /// <param name="name">
+        /// The name of the property.
+        /// </param>
+        /// <param name="value">
+        /// The value of the property.
+        /// </param>
+        public ImageProperty(string name, string value)
+        {
+            this.Name = name;
+            this.Value = value;
+        }
+
+        /// <summary>
+        /// Compares two <see cref="ImageProperty"/> objects. The result specifies whether the values
+        /// of the <see cref="ImageProperty.Name"/> or <see cref="ImageProperty.Value"/> properties of the two
+        /// <see cref="ImageProperty"/> objects are equal.
+        /// </summary>
+        /// <param name="left">
+        /// The <see cref="ImageProperty"/> on the left side of the operand.
+        /// </param>
+        /// <param name="right">
+        /// The <see cref="ImageProperty"/> on the right side of the operand.
+        /// </param>
+        /// <returns>
+        /// True if the current left is equal to the <paramref name="right"/> parameter; otherwise, false.
+        /// </returns>
+        public static bool operator ==(ImageProperty left, ImageProperty right)
+        {
+            return left.Equals(right);
+        }
+
+        /// <summary>
+        /// Compares two <see cref="ImageProperty"/> objects. The result specifies whether the values
+        /// of the <see cref="ImageProperty.Name"/> or <see cref="ImageProperty.Value"/> properties of the two
+        /// <see cref="ImageProperty"/> objects are unequal.
+        /// </summary>
+        /// <param name="left">
+        /// The <see cref="ImageProperty"/> on the left side of the operand.
+        /// </param>
+        /// <param name="right">
+        /// The <see cref="ImageProperty"/> on the right side of the operand.
+        /// </param>
+        /// <returns>
+        /// True if the current left is unequal to the <paramref name="right"/> parameter; otherwise, false.
+        /// </returns>
+        public static bool operator !=(ImageProperty left, ImageProperty right)
+        {
+            return !left.Equals(right);
+        }
+
+        /// <summary>
+        /// Indicates whether this instance and a specified object are equal.
+        /// </summary>
+        /// <param name="obj">
+        /// The object to compare with the current instance. 
+        /// </param>
+        /// <returns>
+        /// true if <paramref name="obj"/> and this instance are the same type and represent the 
+        /// same value; otherwise, false. 
+        /// </returns>
+        public override bool Equals(object obj)
+        {
+            if (!(obj is ImageProperty))
+            {
+                return false;
+            }
+
+            ImageProperty other = (ImageProperty)obj;
+
+            return other.Name == this.Name && other.Value == this.Value;
+        }
+
+        /// <summary>
+        /// Returns the hash code for this instance.
+        /// </summary>
+        /// <returns>
+        /// A 32-bit signed integer that is the hash code for this instance.
+        /// </returns>
+        public override int GetHashCode()
+        {
+            return this.GetHashCode(this);
+        }
+
+        /// <summary>
+        /// Returns the fully qualified type name of this instance.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="T:System.String"/> containing a fully qualified type name.
+        /// </returns>
+        public override string ToString()
+        {
+            return "{Name=" + this.Name + ",Value=" + this.Value + "}";
+        }
+
+        /// <summary>
+        /// Indicates whether the current object is equal to another object of the same type.
+        /// </summary>
+        /// <returns>
+        /// True if the current object is equal to the <paramref name="other"/> parameter; otherwise, false.
+        /// </returns>
+        /// <param name="other">An object to compare with this object.</param>
+        public bool Equals(ImageProperty other)
+        {
+            return this.Name.Equals(other.Name) && this.Value.Equals(other.Value);
+        }
+
+        /// <summary>
+        /// Returns the hash code for this instance.
+        /// </summary>
+        /// <param name="imageProperty">
+        /// The instance of <see cref="ImageProperty"/> to return the hash code for.
+        /// </param>
+        /// <returns>
+        /// A 32-bit signed integer that is the hash code for this instance.
+        /// </returns>
+        private int GetHashCode(ImageProperty imageProperty)
+        {
+            unchecked
+            {
+                int hashCode = imageProperty.Name.GetHashCode();
+                hashCode = (hashCode * 397) ^ imageProperty.Value.GetHashCode();
+                return hashCode;
+            }
+        }
+    }
+}

src/ImageProcessor/Settings.StyleCop

@@ -0,0 +1,12 @@
+<StyleCopSettings Version="105">
+  <GlobalSettings>
+    <CollectionProperty Name="RecognizedWords">
+      <Value>EX</Value>
+      <Value>png</Value>
+      <Value>scanline</Value>
+      <Value>scanlines</Value>
+      <Value>tEXt</Value>
+      <Value>xt</Value>
+    </CollectionProperty>
+  </GlobalSettings>
+</StyleCopSettings>

src/ImageProcessor/packages.config

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<packages>
+  <package id="SharpZipLib.Portable" version="0.86.0.0002" targetFramework="portable-net45+win+wp80" />
+</packages>

tests/ImageProcessor.Tests/Colors/ColorTests.cs

@@ -0,0 +1,102 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="ColorTests.cs" company="James South">
+//   Copyright © James South and contributors.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Tests the <see cref="Color" /> struct.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Tests
+{
+    using Xunit;
+
+    /// <summary>
+    /// Tests the <see cref="Color"/> struct.
+    /// </summary>
+    public class ColorTests
+    {
+        /// <summary>
+        /// Tests the equality operators for equality.
+        /// </summary>
+        [Fact]
+        public void AreEqual()
+        {
+            Color color1 = new Color(0, 0, 0, 255);
+            Color color2 = new Color(0, 0, 0, 255);
+            Color color3 = new Color("#000");
+            Color color4 = new Color("#000000");
+            Color color5 = new Color("#FF000000");
+            Color color6 = new Color(-16777216);
+
+            Assert.Equal(color1, color2);
+            Assert.Equal(color1, color3);
+            Assert.Equal(color1, color4);
+            Assert.Equal(color1, color5);
+            Assert.Equal(color1, color6);
+        }
+
+        /// <summary>
+        /// Tests the equality operators for inequality.
+        /// </summary>
+        [Fact]
+        public void AreNotEqual()
+        {
+            Color color1 = new Color(255, 0, 0, 255);
+            Color color2 = new Color(0, 0, 0, 255);
+            Color color3 = new Color("#000");
+            Color color4 = new Color("#000000");
+            Color color5 = new Color("#FF000000");
+            Color color6 = new Color(-16777216);
+
+            Assert.NotEqual(color1, color2);
+            Assert.NotEqual(color1, color3);
+            Assert.NotEqual(color1, color4);
+            Assert.NotEqual(color1, color5);
+            Assert.NotEqual(color1, color6);
+        }
+
+        /// <summary>
+        /// Tests whether the color constructor correctly assign properties.
+        /// </summary>
+        [Fact]
+        public void ConstructorAssignsProperties()
+        {
+            Color color1 = new Color(255, 10, 34, 220);
+            Assert.Equal(255, color1.B);
+            Assert.Equal(10, color1.G);
+            Assert.Equal(34, color1.R);
+            Assert.Equal(220, color1.A);
+
+            Color color2 = new Color(255, 10, 34);
+            Assert.Equal(255, color2.B);
+            Assert.Equal(10, color2.G);
+            Assert.Equal(34, color2.R);
+            Assert.Equal(255, color2.A);
+
+            Color color3 = new Color(-1);
+            Assert.Equal(255, color3.B);
+            Assert.Equal(255, color3.G);
+            Assert.Equal(255, color3.R);
+            Assert.Equal(255, color3.A);
+
+            Color color4 = new Color("#FF0000");
+            Assert.Equal(0, color4.B);
+            Assert.Equal(0, color4.G);
+            Assert.Equal(255, color4.R);
+            Assert.Equal(255, color4.A);
+        }
+
+        /// <summary>
+        /// Tests to see that in the input hex matches that of the output.
+        /// </summary>
+        [Fact]
+        public void ConvertHex()
+        {
+            const string First = "FF000000";
+            string second = new Color(0, 0, 0, 255).Bgra.ToString("X");
+            Assert.Equal(First, second);
+        }
+    }
+}

tests/ImageProcessor.Tests/ImageProcessor.Tests.csproj

@@ -60,6 +60,7 @@
     <Otherwise />
   </Choose>
   <ItemGroup>
+    <Compile Include="Colors\ColorTests.cs" />
     <Compile Include="Numerics\RectangleTests.cs" />
     <Compile Include="Numerics\PointTests.cs" />
     <Compile Include="Numerics\SizeTests.cs" />

tests/ImageProcessor.Tests/ImageProcessor.Tests.csproj.DotSettings

@@ -1,2 +1,3 @@
 <wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=colors/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=numerics/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>