Merge branch 'master' into GradientBrush

src/ImageSharp/Common/Extensions/ByteExtensions.cs

@@ -1,55 +0,0 @@
-// Copyright (c) Six Labors and contributors.
-// Licensed under the Apache License, Version 2.0.
-
-using System;
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.PixelFormats;
-
-namespace SixLabors.ImageSharp
-{
-    /// <summary>
-    /// Extension methods for the <see cref="byte"/> struct buffers.
-    /// </summary>
-    internal static class ByteExtensions
-    {
-        /// <summary>
-        /// Returns a reference to the given position of the array unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
-        /// </summary>
-        /// <param name="bytes">The byte array.</param>
-        /// <param name="offset">The offset in bytes.</param>
-        /// <returns>The <see cref="ImageSharp.PixelFormats.Rgb24"/> reference at the given offset.</returns>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static ref Rgb24 GetRgb24(this byte[] bytes, int offset)
-        {
-            DebugGuard.MustBeLessThan(offset + 2, bytes.Length, nameof(offset));
-
-            return ref Unsafe.As<byte, Rgb24>(ref bytes[offset]);
-        }
-
-        /// <summary>
-        /// Returns a reference to the given position of the span unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
-        /// </summary>
-        /// <param name="bytes">The byte span.</param>
-        /// <param name="offset">The offset in bytes.</param>
-        /// <returns>The <see cref="ImageSharp.PixelFormats.Rgb24"/> reference at the given offset.</returns>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static ref Rgb24 GetRgb24(this Span<byte> bytes, int offset)
-        {
-            DebugGuard.MustBeLessThan(offset + 2, bytes.Length, nameof(offset));
-
-            return ref Unsafe.As<byte, Rgb24>(ref bytes[offset]);
-        }
-
-        /// <summary>
-        ///  Returns a reference to the given position of the buffer pointed by `baseRef` unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
-        /// </summary>
-        /// <param name="baseRef">A reference to the beginning of the buffer</param>
-        /// <param name="offset">The offset in bytes.</param>
-        /// <returns>The <see cref="ImageSharp.PixelFormats.Rgb24"/> reference at the given offset.</returns>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static ref Rgb24 GetRgb24(ref byte baseRef, int offset)
-        {
-            return ref Unsafe.As<byte, Rgb24>(ref Unsafe.Add(ref baseRef, offset));
-        }
-    }
-}

src/ImageSharp/Common/Helpers/Guard.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Linq;
 
 namespace SixLabors.ImageSharp
 {
@@ -15,78 +14,62 @@ namespace SixLabors.ImageSharp
     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.
+        /// Ensures that the value is not null.
         /// </summary>
-        /// <param name="target">The target object, which cannot be null.</param>
+        /// <param name="value">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 = "")
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is null</exception>
+        public static void NotNull(object value, string parameterName)
         {
-            if (target == null)
+            if (value == 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.
+        /// Ensures that the target value is not null, empty, or whitespace.
         /// </summary>
-        /// <param name="target">The target string, which should be checked against being null or empty.</param>
+        /// <param name="value">The target string, which should be checked against being null or empty.</param>
         /// <param name="parameterName">Name of the parameter.</param>
-        /// <param name="message">The error message, if any to add to the exception.</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, string message = "")
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is null.</exception>
+        /// <exception cref="ArgumentException"><paramref name="value"/> is empty or contains only blanks.</exception>
+        public static void NotNullOrWhiteSpace(string value, string parameterName)
         {
-            NotNull(target, parameterName, message);
-
-            if (string.IsNullOrWhiteSpace(target))
+            if (value == null)
             {
-                if (!string.IsNullOrWhiteSpace(message))
-                {
-                    throw new ArgumentException(message, parameterName);
-                }
+                throw new ArgumentNullException(parameterName);
+            }
 
-                throw new ArgumentException("Value cannot be null or empty and cannot contain only blanks.", parameterName);
+            if (string.IsNullOrWhiteSpace(value))
+            {
+                throw new ArgumentException("Must not be empty or whitespace.", parameterName);
             }
         }
 
         /// <summary>
-        /// Verifies, that the enumeration is not null and not empty.
+        /// Ensures that the enumeration is not null or empty.
         /// </summary>
-        /// <typeparam name="T">The type of objects in the <paramref name="target"/></typeparam>
-        /// <param name="target">The target enumeration, which should be checked against being null or empty.</param>
+        /// <typeparam name="T">The type of objects in the <paramref name="value"/></typeparam>
+        /// <param name="value">The target enumeration, which should be checked against being null or empty.</param>
         /// <param name="parameterName">Name of the parameter.</param>
-        /// <param name="message">The error message, if any to add to the exception.</param>
-        /// <exception cref="ArgumentNullException"><paramref name="target"/> is null.</exception>
-        /// <exception cref="ArgumentException"><paramref name="target"/> is empty.</exception>
-        public static void NotNullOrEmpty<T>(IEnumerable<T> target, string parameterName, string message = "")
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is null.</exception>
+        /// <exception cref="ArgumentException"><paramref name="value"/> is empty.</exception>
+        public static void NotNullOrEmpty<T>(ICollection<T> value, string parameterName)
         {
-            NotNull(target, parameterName, message);
-
-            if (!target.Any())
+            if (value == null)
             {
-                if (!string.IsNullOrWhiteSpace(message))
-                {
-                    throw new ArgumentException(message, parameterName);
-                }
+                throw new ArgumentNullException(parameterName);
+            }
 
-                throw new ArgumentException("Value cannot be empty.", parameterName);
+            if (value.Count == 0)
+            {
+                throw new ArgumentException("Must not be empty.", parameterName);
             }
         }
 
         /// <summary>
-        /// Verifies that the specified value is less than a maximum value
-        /// and throws an exception if it is not.
+        /// Ensures that the specified value is less than a maximum value.
         /// </summary>
         /// <param name="value">The target value, which should be validated.</param>
         /// <param name="max">The maximum value.</param>
@@ -191,15 +174,9 @@ namespace SixLabors.ImageSharp
         /// Verifies, that the method parameter with specified target value is true
         /// and throws an exception if it is found to be so.
         /// </summary>
-        /// <param name="target">
-        /// The target value, which cannot be false.
-        /// </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>
+        /// <param name="target">The target value, which cannot be false.</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="ArgumentException">
         /// <paramref name="target"/> is false
         /// </exception>

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -39,11 +39,6 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// </summary>
         private IManagedByteBuffer globalColorTable;
 
-        /// <summary>
-        /// The global color table length
-        /// </summary>
-        private int globalColorTableLength;
-
         /// <summary>
         /// The area to restore.
         /// </summary>
@@ -333,8 +328,8 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 indices = this.configuration.MemoryManager.AllocateManagedByteBuffer(imageDescriptor.Width * imageDescriptor.Height, true);
 
                 this.ReadFrameIndices(imageDescriptor, indices.Span);
-                IManagedByteBuffer colorTable = localColorTable ?? this.globalColorTable;
-                this.ReadFrameColors(ref image, ref previousFrame, indices.Span, colorTable.Span, imageDescriptor);
+                ReadOnlySpan<Rgb24> colorTable = MemoryMarshal.Cast<byte, Rgb24>((localColorTable ?? this.globalColorTable).Span);
+                this.ReadFrameColors(ref image, ref previousFrame, indices.Span, colorTable, imageDescriptor);
 
                 // Skip any remaining blocks
                 this.Skip(0);
@@ -370,7 +365,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// <param name="indices">The indexed pixels.</param>
         /// <param name="colorTable">The color table containing the available colors.</param>
         /// <param name="descriptor">The <see cref="GifImageDescriptor"/></param>
-        private void ReadFrameColors<TPixel>(ref Image<TPixel> image, ref ImageFrame<TPixel> previousFrame, Span<byte> indices, Span<byte> colorTable, in GifImageDescriptor descriptor)
+        private void ReadFrameColors<TPixel>(ref Image<TPixel> image, ref ImageFrame<TPixel> previousFrame, Span<byte> indices, ReadOnlySpan<Rgb24> colorTable, in GifImageDescriptor descriptor)
             where TPixel : struct, IPixel<TPixel>
         {
             ref byte indicesRef = ref MemoryMarshal.GetReference(indices);
@@ -458,11 +453,8 @@ namespace SixLabors.ImageSharp.Formats.Gif
                     if (this.graphicsControlExtension.TransparencyFlag == false ||
                         this.graphicsControlExtension.TransparencyIndex != index)
                     {
-                        int indexOffset = index * 3;
-
                         ref TPixel pixel = ref Unsafe.Add(ref rowRef, x);
-                        rgba.Rgb = colorTable.GetRgb24(indexOffset);
-
+                        rgba.Rgb = colorTable[index];
                         pixel.PackFromRgba32(rgba);
                     }
 
@@ -534,12 +526,12 @@ namespace SixLabors.ImageSharp.Formats.Gif
 
             if (this.logicalScreenDescriptor.GlobalColorTableFlag)
             {
-                this.globalColorTableLength = this.logicalScreenDescriptor.GlobalColorTableSize * 3;
+                int globalColorTableLength = this.logicalScreenDescriptor.GlobalColorTableSize * 3;
 
-                this.globalColorTable = this.MemoryManager.AllocateManagedByteBuffer(this.globalColorTableLength, true);
+                this.globalColorTable = this.MemoryManager.AllocateManagedByteBuffer(globalColorTableLength, true);
 
-                // Read the global color table from the stream
-                stream.Read(this.globalColorTable.Array, 0, this.globalColorTableLength);
+                // Read the global color table data from the stream
+                stream.Read(this.globalColorTable.Array, 0, globalColorTableLength);
             }
         }
     }

src/ImageSharp/Formats/ImageFormatManager.cs

@@ -85,6 +85,13 @@ namespace SixLabors.ImageSharp.Formats
         /// <returns>The <see cref="IImageFormat"/> if found otherwise null</returns>
         public IImageFormat FindFormatByFileExtension(string extension)
         {
+            Guard.NotNullOrWhiteSpace(extension, nameof(extension));
+
+            if (extension[0] == '.')
+            {
+                extension = extension.Substring(1);
+            }
+
             return this.imageFormats.FirstOrDefault(x => x.FileExtensions.Contains(extension, StringComparer.OrdinalIgnoreCase));
         }
 

src/ImageSharp/Formats/Png/Filters/NoneFilter.cs

@@ -20,7 +20,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters
         /// <param name="scanline">The scanline to encode</param>
         /// <param name="result">The filtered scanline result.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void Encode(Span<byte> scanline, Span<byte> result)
+        public static void Encode(ReadOnlySpan<byte> scanline, Span<byte> result)
         {
             // Insert a byte before the data.
             result[0] = 0;

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -853,7 +853,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             where TPixel : struct, IPixel<TPixel>
         {
             ReadOnlySpan<byte> newScanline = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
-            byte[] pal = this.palette;
+            ReadOnlySpan<Rgb24> pal = MemoryMarshal.Cast<byte, Rgb24>(this.palette);
             var color = default(TPixel);
 
             var rgba = default(Rgba32);
@@ -865,10 +865,9 @@ namespace SixLabors.ImageSharp.Formats.Png
                 for (int x = 0; x < this.header.Width; x++)
                 {
                     int index = newScanline[x];
-                    int pixelOffset = index * 3;
 
                     rgba.A = this.paletteAlpha.Length > index ? this.paletteAlpha[index] : (byte)255;
-                    rgba.Rgb = pal.GetRgb24(pixelOffset);
+                    rgba.Rgb = pal[index];
 
                     color.PackFromRgba32(rgba);
                     row[x] = color;
@@ -881,9 +880,8 @@ namespace SixLabors.ImageSharp.Formats.Png
                 for (int x = 0; x < this.header.Width; x++)
                 {
                     int index = newScanline[x];
-                    int pixelOffset = index * 3;
 
-                    rgba.Rgb = pal.GetRgb24(pixelOffset);
+                    rgba.Rgb = pal[index];
 
                     color.PackFromRgba32(rgba);
                     row[x] = color;
@@ -946,6 +944,7 @@ namespace SixLabors.ImageSharp.Formats.Png
 
                     ReadOnlySpan<byte> newScanline = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
                     var rgba = default(Rgba32);
+                    Span<Rgb24> pal = MemoryMarshal.Cast<byte, Rgb24>(this.palette);
 
                     if (this.paletteAlpha != null && this.paletteAlpha.Length > 0)
                     {
@@ -954,10 +953,9 @@ namespace SixLabors.ImageSharp.Formats.Png
                         for (int x = pixelOffset, o = 0; x < this.header.Width; x += increment, o++)
                         {
                             int index = newScanline[o];
-                            int offset = index * 3;
 
                             rgba.A = this.paletteAlpha.Length > index ? this.paletteAlpha[index] : (byte)255;
-                            rgba.Rgb = this.palette.GetRgb24(offset);
+                            rgba.Rgb = pal[index];
 
                             color.PackFromRgba32(rgba);
                             rowSpan[x] = color;
@@ -970,10 +968,8 @@ namespace SixLabors.ImageSharp.Formats.Png
                         for (int x = pixelOffset, o = 0; x < this.header.Width; x += increment, o++)
                         {
                             int index = newScanline[o];
-                            int offset = index * 3;
-
-                            rgba.Rgb = this.palette.GetRgb24(offset);
 
+                            rgba.Rgb = pal[index];
                             color.PackFromRgba32(rgba);
                             rowSpan[x] = color;
                         }

src/ImageSharp/Image.LoadPixelData.cs

@@ -33,7 +33,7 @@ namespace SixLabors.ImageSharp
         /// <param name="height">The height of the final image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
-        private static Image<TPixel> LoadPixelData<TPixel>(Span<TPixel> data, int width, int height)
+        public static Image<TPixel> LoadPixelData<TPixel>(ReadOnlySpan<TPixel> data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
             => LoadPixelData(Configuration.Default, data, width, height);
 
@@ -57,7 +57,7 @@ namespace SixLabors.ImageSharp
         /// <param name="height">The height of the final image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
-        private static Image<TPixel> LoadPixelData<TPixel>(Span<byte> data, int width, int height)
+        public static Image<TPixel> LoadPixelData<TPixel>(ReadOnlySpan<byte> data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
             => LoadPixelData<TPixel>(Configuration.Default, data, width, height);
 
@@ -72,7 +72,7 @@ namespace SixLabors.ImageSharp
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
         public static Image<TPixel> LoadPixelData<TPixel>(Configuration config, byte[] data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
-            => LoadPixelData(config, MemoryMarshal.Cast<byte, TPixel>(data.AsSpan()), width, height);
+            => LoadPixelData(config, MemoryMarshal.Cast<byte, TPixel>(new ReadOnlySpan<byte>(data)), width, height);
 
         /// <summary>
         /// Create a new instance of the <see cref="Image{TPixel}"/> class from the given byte array in <typeparamref name="TPixel"/> format.
@@ -83,7 +83,7 @@ namespace SixLabors.ImageSharp
         /// <param name="height">The height of the final image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
-        private static Image<TPixel> LoadPixelData<TPixel>(Configuration config, Span<byte> data, int width, int height)
+        public static Image<TPixel> LoadPixelData<TPixel>(Configuration config, ReadOnlySpan<byte> data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
             => LoadPixelData(config, MemoryMarshal.Cast<byte, TPixel>(data), width, height);
 
@@ -99,7 +99,7 @@ namespace SixLabors.ImageSharp
         public static Image<TPixel> LoadPixelData<TPixel>(Configuration config, TPixel[] data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
         {
-            return LoadPixelData(config, data.AsSpan(), width, height);
+            return LoadPixelData(config, new ReadOnlySpan<TPixel>(data), width, height);
         }
 
         /// <summary>
@@ -111,7 +111,7 @@ namespace SixLabors.ImageSharp
         /// <param name="height">The height of the final image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
-        private static Image<TPixel> LoadPixelData<TPixel>(Configuration config, Span<TPixel> data, int width, int height)
+        public static Image<TPixel> LoadPixelData<TPixel>(Configuration config, ReadOnlySpan<TPixel> data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
         {
             int count = width * height;

src/ImageSharp/ImageExtensions.cs

@@ -4,13 +4,11 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.PixelFormats;
-using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp
 {
@@ -21,18 +19,18 @@ namespace SixLabors.ImageSharp
     {
 #if !NETSTANDARD1_1
         /// <summary>
-        /// Saves the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given stream using the currently loaded image format.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
-        /// <param name="source">The source image</param>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="source">The source image.</param>
         /// <param name="filePath">The file path to save the image to.</param>
         /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
         public static void Save<TPixel>(this Image<TPixel> source, string filePath)
             where TPixel : struct, IPixel<TPixel>
         {
-            Guard.NotNullOrEmpty(filePath, nameof(filePath));
+            Guard.NotNullOrWhiteSpace(filePath, nameof(filePath));
 
-            string ext = Path.GetExtension(filePath).Trim('.');
+            string ext = Path.GetExtension(filePath);
             IImageFormat format = source.GetConfiguration().ImageFormatsManager.FindFormatByFileExtension(ext);
             if (format == null)
             {
@@ -64,13 +62,13 @@ namespace SixLabors.ImageSharp
         }
 
         /// <summary>
-        /// Saves the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given stream using the currently loaded image format.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
-        /// <param name="source">The source image</param>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="source">The source image.</param>
         /// <param name="filePath">The file path to save the image to.</param>
         /// <param name="encoder">The encoder to save the image with.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the encoder is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the encoder is null.</exception>
         public static void Save<TPixel>(this Image<TPixel> source, string filePath, IImageEncoder encoder)
             where TPixel : struct, IPixel<TPixel>
         {
@@ -83,13 +81,13 @@ namespace SixLabors.ImageSharp
 #endif
 
         /// <summary>
-        /// Saves the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given stream using the currently loaded image format.
         /// </summary>
         /// <typeparam name="TPixel">The Pixel format.</typeparam>
-        /// <param name="source">The source image</param>
+        /// <param name="source">The source image.</param>
         /// <param name="stream">The stream to save the image to.</param>
-        /// <param name="format">The format to save the image to.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <param name="format">The format to save the image in.</param>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static void Save<TPixel>(this Image<TPixel> source, Stream stream, IImageFormat format)
             where TPixel : struct, IPixel<TPixel>
         {
@@ -113,67 +111,67 @@ namespace SixLabors.ImageSharp
         }
 
         /// <summary>
-        /// Saves the raw image pixels to a byte array in row-major order.
+        /// Returns the a copy of the image pixels as a byte array in row-major order.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The source image</param>
         /// <returns>A copy of the pixel data as bytes from this frame.</returns>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static byte[] SavePixelData<TPixel>(this ImageFrame<TPixel> source)
             where TPixel : struct, IPixel<TPixel>
          => MemoryMarshal.AsBytes(source.GetPixelSpan()).ToArray();
 
         /// <summary>
-        /// Saves the raw image pixels to the given byte array in row-major order.
+        /// Writes the raw image pixels to the given byte array in row-major order.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
-        /// <param name="source">The source image</param>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="source">The source image.</param>
         /// <param name="buffer">The buffer to save the raw pixel data to.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static void SavePixelData<TPixel>(this ImageFrame<TPixel> source, byte[] buffer)
             where TPixel : struct, IPixel<TPixel>
             => SavePixelData(source, MemoryMarshal.Cast<byte, TPixel>(buffer.AsSpan()));
 
         /// <summary>
-        /// Saves the raw image pixels to the given TPixel array in row-major order.
+        /// Writes the raw image pixels to the given TPixel array in row-major order.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The source image</param>
         /// <param name="buffer">The buffer to save the raw pixel data to.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static void SavePixelData<TPixel>(this ImageFrame<TPixel> source, TPixel[] buffer)
             where TPixel : struct, IPixel<TPixel>
             => SavePixelData(source, buffer.AsSpan());
 
         /// <summary>
-        /// Saves the raw image pixels to a byte array in row-major order.
+        /// Returns a copy of the raw image pixels as a byte array in row-major order.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
-        /// <param name="source">The source image</param>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="source">The source image.</param>
         /// <returns>A copy of the pixel data from the first frame as bytes.</returns>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static byte[] SavePixelData<TPixel>(this Image<TPixel> source)
             where TPixel : struct, IPixel<TPixel>
          => source.Frames.RootFrame.SavePixelData();
 
         /// <summary>
-        /// Saves the raw image pixels to the given byte array in row-major order.
+        /// Writes the raw image pixels to the given byte array in row-major order.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
-        /// <param name="source">The source image</param>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="source">The source image.</param>
         /// <param name="buffer">The buffer to save the raw pixel data to.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static void SavePixelData<TPixel>(this Image<TPixel> source, byte[] buffer)
             where TPixel : struct, IPixel<TPixel>
             => source.Frames.RootFrame.SavePixelData(buffer);
 
         /// <summary>
-        /// Saves the raw image pixels to the given TPixel array in row-major order.
+        /// Writes the raw image pixels to the given TPixel array in row-major order.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The source image</param>
         /// <param name="buffer">The buffer to save the raw pixel data to.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if the stream is null.</exception>
         public static void SavePixelData<TPixel>(this Image<TPixel> source, TPixel[] buffer)
             where TPixel : struct, IPixel<TPixel>
             => source.Frames.RootFrame.SavePixelData(buffer);
@@ -182,7 +180,7 @@ namespace SixLabors.ImageSharp
         /// Returns a Base64 encoded string from the given image.
         /// </summary>
         /// <example><see href="data:image/gif;base64,R0lGODlhAQABAIABAEdJRgAAACwAAAAAAQABAAACAkQBAA=="/></example>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The source image</param>
         /// <param name="format">The format.</param>
         /// <returns>The <see cref="string"/></returns>
@@ -198,24 +196,24 @@ namespace SixLabors.ImageSharp
         }
 
         /// <summary>
-        /// Saves the raw image to the given bytes.
+        /// Writes the raw image bytes to the given byte span.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The source image</param>
-        /// <param name="buffer">The buffer to save the raw pixel data to.</param>
+        /// <param name="buffer">The span to save the raw pixel data to.</param>
         /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
-        internal static void SavePixelData<TPixel>(this Image<TPixel> source, Span<byte> buffer)
+        public static void SavePixelData<TPixel>(this Image<TPixel> source, Span<byte> buffer)
             where TPixel : struct, IPixel<TPixel>
             => source.Frames.RootFrame.SavePixelData(MemoryMarshal.Cast<byte, TPixel>(buffer));
 
         /// <summary>
-        /// Saves the raw image to the given bytes.
+        /// Writes the raw image pixels to the given TPixel span.
         /// </summary>
-        /// <typeparam name="TPixel">The Pixel format.</typeparam>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The source image</param>
-        /// <param name="buffer">The buffer to save the raw pixel data to.</param>
+        /// <param name="buffer">The span to save the raw pixel data to.</param>
         /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
-        internal static void SavePixelData<TPixel>(this ImageFrame<TPixel> source, Span<TPixel> buffer)
+        public static void SavePixelData<TPixel>(this ImageFrame<TPixel> source, Span<TPixel> buffer)
             where TPixel : struct, IPixel<TPixel>
         {
             Span<TPixel> sourceBuffer = source.GetPixelSpan();
@@ -224,4 +222,4 @@ namespace SixLabors.ImageSharp
             sourceBuffer.CopyTo(buffer);
         }
     }
-}
+}

src/ImageSharp/ImageFrame.LoadPixelData.cs

@@ -23,7 +23,7 @@ namespace SixLabors.ImageSharp
         /// <param name="height">The height of the final image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
-        public static ImageFrame<TPixel> LoadPixelData<TPixel>(MemoryManager memoryManager, Span<byte> data, int width, int height)
+        public static ImageFrame<TPixel> LoadPixelData<TPixel>(MemoryManager memoryManager, ReadOnlySpan<byte> data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
             => LoadPixelData(memoryManager, MemoryMarshal.Cast<byte, TPixel>(data), width, height);
 
@@ -36,7 +36,7 @@ namespace SixLabors.ImageSharp
         /// <param name="height">The height of the final image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <returns>A new <see cref="Image{TPixel}"/>.</returns>
-        public static ImageFrame<TPixel> LoadPixelData<TPixel>(MemoryManager memoryManager, Span<TPixel> data, int width, int height)
+        public static ImageFrame<TPixel> LoadPixelData<TPixel>(MemoryManager memoryManager, ReadOnlySpan<TPixel> data, int width, int height)
             where TPixel : struct, IPixel<TPixel>
         {
             int count = width * height;

src/ImageSharp/ImageFrameCollection.cs

@@ -32,7 +32,7 @@ namespace SixLabors.ImageSharp
         internal ImageFrameCollection(Image<TPixel> parent, IEnumerable<ImageFrame<TPixel>> frames)
         {
             Guard.NotNull(parent, nameof(parent));
-            Guard.NotNullOrEmpty(frames, nameof(frames));
+            Guard.NotNull(frames, nameof(frames));
 
             this.parent = parent;
 
@@ -42,6 +42,12 @@ namespace SixLabors.ImageSharp
                 this.ValidateFrame(f);
                 this.frames.Add(f);
             }
+
+            // Ensure at least 1 frame was added to the frames collection
+            if (this.frames.Count == 0)
+            {
+                throw new ArgumentException("Must not be empty.", nameof(frames));
+            }
         }
 
         /// <summary>
@@ -111,7 +117,7 @@ namespace SixLabors.ImageSharp
 
             var frame = ImageFrame.LoadPixelData(
                 this.parent.GetMemoryManager(),
-                new Span<TPixel>(source),
+                new ReadOnlySpan<TPixel>(source),
                 this.RootFrame.Width,
                 this.RootFrame.Height);
             this.frames.Add(frame);

src/ImageSharp/MetaData/ImageProperty.cs

@@ -19,7 +19,7 @@ namespace SixLabors.ImageSharp.MetaData
         /// <param name="value">The value of the property.</param>
         public ImageProperty(string name, string value)
         {
-            Guard.NotNullOrEmpty(name, nameof(name));
+            Guard.NotNullOrWhiteSpace(name, nameof(name));
 
             this.Name = name;
             this.Value = value;

src/ImageSharp/PixelFormats/ColorBuilder{TPixel}.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers.Binary;
 using System.Globalization;
 
 namespace SixLabors.ImageSharp.PixelFormats
@@ -23,21 +24,17 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <returns>Returns a <typeparamref name="TPixel"/> that represents the color defined by the provided RGBA heax string.</returns>
         public static TPixel FromHex(string hex)
         {
-            Guard.NotNullOrEmpty(hex, nameof(hex));
+            Guard.NotNullOrWhiteSpace(hex, nameof(hex));
 
             hex = ToRgbaHex(hex);
-            uint packedValue;
-            if (hex == null || !uint.TryParse(hex, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out packedValue))
+
+            if (hex == null || !uint.TryParse(hex, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out uint packedValue))
             {
                 throw new ArgumentException("Hexadecimal string is not in the correct format.", nameof(hex));
             }
 
             TPixel result = default;
-            var rgba = new Rgba32(
-                (byte)(packedValue >> 24),
-                (byte)(packedValue >> 16),
-                (byte)(packedValue >> 8),
-                (byte)(packedValue >> 0));
+            var rgba = new Rgba32(BinaryPrimitives.ReverseEndianness(packedValue));
 
             result.PackFromRgba32(rgba);
             return result;
@@ -76,7 +73,10 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// </returns>
         private static string ToRgbaHex(string hex)
         {
-            hex = hex.StartsWith("#") ? hex.Substring(1) : hex;
+            if (hex[0] == '#')
+            {
+                hex = hex.Substring(1);
+            }
 
             if (hex.Length == 8)
             {
@@ -93,12 +93,12 @@ namespace SixLabors.ImageSharp.PixelFormats
                 return null;
             }
 
-            string red = char.ToString(hex[0]);
-            string green = char.ToString(hex[1]);
-            string blue = char.ToString(hex[2]);
-            string alpha = hex.Length == 3 ? "F" : char.ToString(hex[3]);
+            char r = hex[0];
+            char g = hex[1];
+            char b = hex[2];
+            char a = hex.Length == 3 ? 'F' : hex[3];
 
-            return string.Concat(red, red, green, green, blue, blue, alpha, alpha);
+            return new string(new[] { r, r, g, g, b, b, a, a });
         }
     }
 }

tests/ImageSharp.Tests/Helpers/GuardTests.cs

@@ -35,27 +35,27 @@ namespace SixLabors.ImageSharp.Tests.Helpers
         /// </summary>
         [Fact]
         [SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1122:UseStringEmptyForEmptyStrings", Justification = "Reviewed. Suppression is OK here.")]
-        public void NotEmptyThrowsWhenEmpty()
+        public void NotEmptyOrWhiteSpaceThrowsWhenEmpty()
         {
-            Assert.Throws<ArgumentException>(() => Guard.NotNullOrEmpty("", string.Empty));
+            Assert.Throws<ArgumentException>(() => Guard.NotNullOrWhiteSpace("", string.Empty));
         }
 
         /// <summary>
         /// Tests that the <see cref="M:Guard.NotEmpty"/> method throws when the argument is whitespace.
         /// </summary>
         [Fact]
-        public void NotEmptyThrowsWhenWhitespace()
+        public void NotEmptyOrWhiteSpaceThrowsOnWhitespace()
         {
-            Assert.Throws<ArgumentException>(() => Guard.NotNullOrEmpty(" ", string.Empty));
+            Assert.Throws<ArgumentException>(() => Guard.NotNullOrWhiteSpace(" ", string.Empty));
         }
 
         /// <summary>
         /// Tests that the <see cref="M:Guard.NotEmpty"/> method throws when the argument name is null.
         /// </summary>
         [Fact]
-        public void NotEmptyThrowsWhenParameterNameNull()
+        public void NotEmptyOrWhiteSpaceThrowsWhenParameterNameNull()
         {
-            Assert.Throws<ArgumentNullException>(() => Guard.NotNullOrEmpty(null, null));
+            Assert.Throws<ArgumentNullException>(() => Guard.NotNullOrWhiteSpace(null, null));
         }
 
         /// <summary>

tests/ImageSharp.Tests/PixelFormats/ColorBuilderTests.cs

@@ -0,0 +1,40 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using SixLabors.ImageSharp.PixelFormats;
+
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests.Colors
+{
+    public class ColorBuilderTests
+    {
+        [Fact]
+        public void ParseShortHex()
+        {
+            Assert.Equal(new Rgb24(255, 255, 255), ColorBuilder<Rgb24>.FromHex("#fff"));
+            Assert.Equal(new Rgb24(255, 255, 255), ColorBuilder<Rgb24>.FromHex("fff"));
+            Assert.Equal(new Rgba32(0, 0, 0, 255), ColorBuilder<Rgba32>.FromHex("000f"));
+        }
+
+        [Fact]
+        public void ParseHexLeadingPoundIsOptional()
+        {
+            Assert.Equal(new Rgb24(0, 128, 128), ColorBuilder<Rgb24>.FromHex("#008080"));
+            Assert.Equal(new Rgb24(0, 128, 128), ColorBuilder<Rgb24>.FromHex("008080"));
+        }
+
+        [Fact]
+        public void ParseHexThrowsOnEmpty()
+        {
+            Assert.Throws<ArgumentException>(() => ColorBuilder<Rgb24>.FromHex(""));
+        }
+
+        [Fact]
+        public void ParseHexThrowsOnNull()
+        {
+            Assert.Throws<ArgumentNullException>(() => ColorBuilder<Rgb24>.FromHex(null));
+        }
+    }
+}

tests/ImageSharp.Tests/TestUtilities/TestEnvironment.Formats.cs

@@ -32,8 +32,8 @@ namespace SixLabors.ImageSharp.Tests
 
         internal static IImageFormat GetImageFormat(string filePath)
         {
-            string extension = Path.GetExtension(filePath).ToLower();
-            if (extension[0] == '.') extension = extension.Substring(1);
+            string extension = Path.GetExtension(filePath);
+            
             IImageFormat format = Configuration.ImageFormatsManager.FindFormatByFileExtension(extension);
             return format;
         }