Add more filter methods to API

Former-commit-id: d6ae1aee8613ad004d76fba528cd1bc7a2ca3054
Former-commit-id: 77bb86b4723c5074860e3fd8574115dc21380c04
Former-commit-id: dca053caa530602fd33a3805192e7060df900515

src/ImageProcessor/Common/Exceptions/ImageFormatException.cs

@@ -1,13 +1,7 @@
-// --------------------------------------------------------------------------------------------------------------------
-// <copyright file="ImageFormatException.cs" company="James South">
-//   Copyright (c) James South and contributors.
-//   Licensed under the Apache License, Version 2.0.
+// <copyright file="ImageFormatException.cs" company="James South">
+// Copyright (c) James South and contributors.
+// Licensed under the Apache License, Version 2.0.
 // </copyright>
-// <summary>
-//   The exception that is thrown when the library tries to load
-//   an image, which has an invalid format.
-// </summary>
-// --------------------------------------------------------------------------------------------------------------------
 
 namespace ImageProcessor
 {
@@ -27,7 +21,7 @@ namespace ImageProcessor
         }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="ImageFormatException"/> class with the name of the 
+        /// Initializes a new instance of the <see cref="ImageFormatException"/> class with the name of the
         /// parameter that causes this exception.
         /// </summary>
         /// <param name="errorMessage">The error message that explains the reason for this exception.</param>
@@ -37,11 +31,11 @@ namespace ImageProcessor
         }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="ImageFormatException"/> class with a specified 
+        /// Initializes a new instance of the <see cref="ImageFormatException"/> class with a specified
         /// error message and the exception that is the cause of this exception.
         /// </summary>
         /// <param name="errorMessage">The error message that explains the reason for this exception.</param>
-        /// <param name="innerException">The exception that is the cause of the current exception, or a null reference (Nothing in Visual Basic) 
+        /// <param name="innerException">The exception that is the cause of the current exception, or a null reference (Nothing in Visual Basic)
         /// if no inner exception is specified.</param>
         public ImageFormatException(string errorMessage, Exception innerException)
             : base(errorMessage, innerException)

src/ImageProcessor/Filters/ColorMatrix/GreyscaleMode.cs

@@ -0,0 +1,23 @@
+// <copyright file="GreyscaleMode.cs" company="James South">
+// Copyright (c) James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Filters
+{
+    /// <summary>
+    /// Provides enumeration over the various greyscale methods available.
+    /// </summary>
+    public enum GreyscaleMode
+    {
+        /// <summary>
+        /// ITU-R Recommendation BT.709
+        /// </summary>
+        Bt709,
+
+        /// <summary>
+        /// ITU-R Recommendation BT.601
+        /// </summary>
+        Bt601
+    }
+}

src/ImageProcessor/Filters/ImageFilterExtensions.cs

@@ -10,6 +10,31 @@ namespace ImageProcessor.Filters
     /// </summary>
     public static class ImageFilterExtensions
     {
+        /// <summary>
+        /// Alters the alpha component of the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="percent">The new opacity of the image. Must be between 0 and 100.</param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image Alpha(this Image source, int percent)
+        {
+            return Alpha(source, percent, source.Bounds);
+        }
+
+        /// <summary>
+        /// Alters the alpha component of the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="percent">The new opacity of the image. Must be between 0 and 100.</param>
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
+        /// </param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image Alpha(this Image source, int percent, Rectangle rectangle)
+        {
+            return source.Process(rectangle, new Alpha(percent));
+        }
+
         /// <summary>
         /// Alters the contrast component of the image.
         /// </summary>
@@ -26,61 +51,109 @@ namespace ImageProcessor.Filters
         /// </summary>
         /// <param name="source">The image this method extends.</param>
         /// <param name="amount">The new contrast of the image. Must be between -100 and 100.</param>
-        /// <param name="sourceRectangle">
-        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to draw.
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
         /// </param>
         /// <returns>The <see cref="Image"/>.</returns>
-        public static Image Contrast(this Image source, int amount, Rectangle sourceRectangle)
+        public static Image Contrast(this Image source, int amount, Rectangle rectangle)
         {
-            return source.Process(sourceRectangle, new Contrast(amount));
+            return source.Process(rectangle, new Contrast(amount));
         }
 
         /// <summary>
-        /// Alters the alpha component of the image.
+        /// Inverts the colors of the image.
         /// </summary>
         /// <param name="source">The image this method extends.</param>
-        /// <param name="percent">The new opacity of the image. Must be between 0 and 100.</param>
         /// <returns>The <see cref="Image"/>.</returns>
-        public static Image Alpha(this Image source, int percent)
+        public static Image Invert(this Image source)
         {
-            return Alpha(source, percent, source.Bounds);
+            return Invert(source, source.Bounds);
         }
 
         /// <summary>
-        /// Alters the alpha component of the image.
+        /// Inverts the colors of the image.
         /// </summary>
         /// <param name="source">The image this method extends.</param>
-        /// <param name="percent">The new opacity of the image. Must be between 0 and 100.</param>
-        /// <param name="sourceRectangle">
-        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to draw.
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
         /// </param>
         /// <returns>The <see cref="Image"/>.</returns>
-        public static Image Alpha(this Image source, int percent, Rectangle sourceRectangle)
+        public static Image Invert(this Image source, Rectangle rectangle)
         {
-            return source.Process(sourceRectangle, new Alpha(percent));
+            return source.Process(rectangle, new Invert());
         }
 
         /// <summary>
-        /// Alters the alpha component of the image.
+        /// Applies sepia toning to the image.
         /// </summary>
         /// <param name="source">The image this method extends.</param>
         /// <returns>The <see cref="Image"/>.</returns>
-        public static Image Invert(this Image source)
+        public static Image Sepia(this Image source)
         {
-            return Invert(source, source.Bounds);
+            return Sepia(source, source.Bounds);
         }
 
         /// <summary>
-        /// Alters the alpha component of the image.
+        /// Applies sepia toning to the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
+        /// </param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image Sepia(this Image source, Rectangle rectangle)
+        {
+            return source.Process(rectangle, new Sepia());
+        }
+
+        /// <summary>
+        /// Applies black and white toning to the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image BlackWhite(this Image source)
+        {
+            return BlackWhite(source, source.Bounds);
+        }
+
+        /// <summary>
+        /// Applies black and white toning to the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
+        /// </param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image BlackWhite(this Image source, Rectangle rectangle)
+        {
+            return source.Process(rectangle, new BlackWhite());
+        }
+
+        /// <summary>
+        /// Applies greyscale toning to the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="mode">The formula to apply to perform the operation.</param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image Greyscale(this Image source, GreyscaleMode mode = GreyscaleMode.Bt709)
+        {
+            return Greyscale(source, source.Bounds, mode);
+        }
+
+        /// <summary>
+        /// Applies greyscale toning to the image.
         /// </summary>
         /// <param name="source">The image this method extends.</param>
-        /// <param name="sourceRectangle">
-        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to draw.
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
         /// </param>
+        /// <param name="mode">The formula to apply to perform the operation.</param>
         /// <returns>The <see cref="Image"/>.</returns>
-        public static Image Invert(this Image source, Rectangle sourceRectangle)
+        public static Image Greyscale(this Image source, Rectangle rectangle, GreyscaleMode mode = GreyscaleMode.Bt709)
         {
-            return source.Process(sourceRectangle, new Invert());
+            return mode == GreyscaleMode.Bt709
+                ? source.Process(rectangle, new GreyscaleBt709())
+                : source.Process(rectangle, new GreyscaleBt601());
         }
     }
 }

src/ImageProcessor/Formats/IImageDecoder.cs

@@ -1,12 +1,7 @@
-// --------------------------------------------------------------------------------------------------------------------
-// <copyright file="IImageDecoder.cs" company="James South">
-//   Copyright (c) James South and contributors.
-//   Licensed under the Apache License, Version 2.0.
+// <copyright file="IImageDecoder.cs" company="James South">
+// Copyright (c) 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
 {

src/ImageProcessor/Samplers/Resize.cs

@@ -17,7 +17,7 @@ namespace ImageProcessor.Samplers
         /// <summary>
         /// The epsilon for comparing floating point numbers.
         /// </summary>
-        private const float Epsilon = 0.0000001f;
+        private const float Epsilon = 0.00001f;
 
         /// <summary>
         /// The horizontal weights.
@@ -99,6 +99,11 @@ namespace ImageProcessor.Samplers
                                     int originX = xw.Index;
                                     Color sourceColor = PixelOperations.ToLinear(source[originX, originY]);
 
+                                    if (Math.Abs(sourceColor.A) < Epsilon)
+                                    {
+                                        continue;
+                                    }
+
                                     float weight = (yw.Value / verticalSum) * (xw.Value / horizontalSum);
 
                                     destination.R += sourceColor.R * weight;