Add Hue Fixes #262

Also fix sepia to conform to SVG spec


Former-commit-id: 9008d1d7849dc03c16877066b4e1d77fb944fce9
Former-commit-id: 5e70101c6ee320f0525021d4b42c8b7febc982f1
Former-commit-id: b36f5d0afa5baa727682012c395a0729b62c1419

README.md

@@ -80,7 +80,7 @@ git clone https://github.com/JimBobSquarePants/ImageProcessor
  - [x] Entropy Crop
 - Rotation
  - [ ] Flip (90, 270, FlipType etc. Need help) [#261](https://github.com/JimBobSquarePants/ImageProcessor/issues/261)
- - [] Rotate by angle (Need help with Paeth approach) [#258](https://github.com/JimBobSquarePants/ImageProcessor/issues/258)
+ - [ ] Rotate by angle (Need help with Paeth approach) [#258](https://github.com/JimBobSquarePants/ImageProcessor/issues/258)
 - ColorMatrix operations (Uses Matrix4x4)
  - [x] BlackWhite
  - [x] Greyscale BT709
@@ -111,7 +111,7 @@ git clone https://github.com/JimBobSquarePants/ImageProcessor
  - [x] Brightness
  - [x] Pixelate
  - [x] Saturation
- - [ ] Hue [#262](https://github.com/JimBobSquarePants/ImageProcessor/issues/262)
+ - [x] Hue
  - [x] Blend
  - [ ] Mask
 - Effects

src/ImageProcessor/Filters/ColorMatrix/ColorMatrixFilter.cs

@@ -16,6 +16,9 @@ namespace ImageProcessor.Filters
         /// <inheritdoc/>
         public abstract Matrix4x4 Matrix { get; }
 
+        /// <inheritdoc/>
+        public virtual bool Compand => true;
+
         /// <inheritdoc/>
         protected override void Apply(ImageBase target, ImageBase source, Rectangle targetRectangle, Rectangle sourceRectangle, int startY, int endY)
         {
@@ -34,7 +37,7 @@ namespace ImageProcessor.Filters
                         {
                             for (int x = startX; x < endX; x++)
                             {
-                                target[x, y] = ApplyMatrix(source[x, y], matrix);
+                                target[x, y] = this.ApplyMatrix(source[x, y], matrix);
                             }
                         }
                     });
@@ -48,9 +51,14 @@ namespace ImageProcessor.Filters
         /// <returns>
         /// The <see cref="Color"/>.
         /// </returns>
-        private static Color ApplyMatrix(Color color, Matrix4x4 matrix)
+        private Color ApplyMatrix(Color color, Matrix4x4 matrix)
         {
-            color = Color.InverseCompand(color);
+            bool compand = this.Compand;
+
+            if (compand)
+            {
+                color = Color.InverseCompand(color);
+            }
 
             float sr = color.R;
             float sg = color.G;
@@ -60,7 +68,7 @@ namespace ImageProcessor.Filters
             color.G = (sr * matrix.M12) + (sg * matrix.M22) + (sb * matrix.M32) + matrix.M42;
             color.B = (sr * matrix.M13) + (sg * matrix.M23) + (sb * matrix.M33) + matrix.M43;
 
-            return Color.Compand(color);
+            return compand ? Color.Compand(color) : color;
         }
     }
 }

src/ImageProcessor/Filters/Hue.cs → src/ImageProcessor/Filters/ColorMatrix/Hue.cs

@@ -36,31 +36,38 @@
         /// <inheritdoc/>
         public override Matrix4x4 Matrix => this.matrix;
 
+        /// <inheritdoc/>
+        public override bool Compand => false;
+
         /// <inheritdoc/>
         protected override void OnApply(ImageBase source, ImageBase target, Rectangle targetRectangle, Rectangle sourceRectangle)
         {
-            float degrees = this.Angle;
-            double costheta = Math.Cos(degrees);
-            double sintheta = Math.Sin(degrees);
+            float radians = (float)ImageMaths.DegreesToRadians(this.Angle);
+            double cosradians = Math.Cos(radians);
+            double sinradians = Math.Sin(radians);
+
             float lumR = .213f;
             float lumG = .715f;
             float lumB = .072f;
 
+            float oneMinusLumR = 1 - lumR;
+            float oneMinusLumG = 1 - lumG;
+            float oneMinusLumB = 1 - lumB;
+
             // The matrix is set up to preserve the luminance of the image.
             // See http://graficaobscura.com/matrix/index.html
             // Number are taken from https://msdn.microsoft.com/en-us/library/jj192162(v=vs.85).aspx
-            // TODO: This isn't correct. Need to double check MS numbers against maths.
             Matrix4x4 matrix4X4 = new Matrix4x4()
             {
-                M11 = (float)(.213 + (costheta * .787) - (sintheta * .213)),
-                M12 = (float)(.715 - (costheta * .715) - (sintheta * .715)),
-                M13 = (float)(.072 - (costheta * .072) + (sintheta * .928)),
-                M21 = (float)(.213 - (costheta * .213) + (sintheta * .143)),
-                M22 = (float)(.715 + (costheta * .285) + (sintheta * .140)),
-                M23 = (float)(.072 - (costheta * .072) - (sintheta * .283)),
-                M31 = (float)(.213 - (costheta * .213) - (sintheta * .787)),
-                M32 = (float)(.715 - (costheta * .715) + (sintheta * .715)),
-                M33 = (float)(.072 + (costheta * .928) + (sintheta * .072))
+                M11 = (float)(+lumR + (cosradians * oneMinusLumR) - (sinradians * lumR)),
+                M12 = (float)(+lumR - (cosradians * lumR) - (sinradians * lumR)),
+                M13 = (float)(+lumR - (cosradians * lumR) - (sinradians * 0.787)),
+                M21 = (float)(+lumG - (cosradians * lumG) - (sinradians * lumG)),
+                M22 = (float)(+lumG + (cosradians * oneMinusLumG) + (sinradians * 0.140)),
+                M23 = (float)(+lumG - (cosradians * lumG) + (sinradians * lumG)),
+                M31 = (float)(+lumB - (cosradians * lumB) + (sinradians * oneMinusLumB)),
+                M32 = (float)(+lumB - (cosradians * lumB) - (sinradians * 0.283)),
+                M33 = (float)(+lumB + (cosradians * oneMinusLumB) + (sinradians * lumB))
             };
 
             this.matrix = matrix4X4;

src/ImageProcessor/Filters/ColorMatrix/IColorMatrixFilter.cs

@@ -17,5 +17,10 @@ namespace ImageProcessor.Filters
         /// Gets the <see cref="Matrix4x4"/> used to alter the image.
         /// </summary>
         Matrix4x4 Matrix { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether to compand the value on processing.
+        /// </summary>
+        bool Compand { get; }
     }
 }

src/ImageProcessor/Filters/ColorMatrix/Sepia.cs

@@ -8,7 +8,8 @@ namespace ImageProcessor.Filters
     using System.Numerics;
 
     /// <summary>
-    /// Converts the colors of the image to their sepia equivalent recreating an old photo effect.
+    /// Converts the colors of the image to their sepia equivalent.
+    /// The formula used matches the svg specification. <see href="http://www.w3.org/TR/filter-effects/#sepiaEquivalent"/>
     /// </summary>
     public class Sepia : ColorMatrixFilter
     {
@@ -25,5 +26,8 @@ namespace ImageProcessor.Filters
             M32 = .168f,
             M33 = .131f
         };
+
+        /// <inheritdoc/>
+        public override bool Compand => false;
     }
 }

src/ImageProcessor/Filters/ImageFilterExtensions.cs

@@ -209,6 +209,31 @@ namespace ImageProcessor.Filters
                 : source.Process(rectangle, new GreyscaleBt601());
         }
 
+        /// <summary>
+        /// Alters the hue component of the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="degrees">The angle in degrees to adjust the image.</param>
+        /// <returns>The <see cref="Image"/>.</returns>
+        public static Image Hue(this Image source, float degrees)
+        {
+            return Hue(source, degrees, source.Bounds);
+        }
+
+        /// <summary>
+        /// Alters the hue component of the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="degrees">The angle in degrees to adjust the image.</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 Hue(this Image source, float degrees, Rectangle rectangle)
+        {
+            return source.Process(rectangle, new Hue(degrees));
+        }
+
         /// <summary>
         /// Inverts the colors of the image.
         /// </summary>

tests/ImageProcessor.Tests/Processors/Filters/FilterTests.cs

@@ -41,7 +41,9 @@ namespace ImageProcessor.Tests
             { "Sobel", new Sobel {Greyscale = true} },
             { "Pixelate", new Pixelate(8)  },
             { "GuassianBlur", new GuassianBlur(10) },
-            { "GuassianSharpen", new GuassianSharpen(10) }
+            { "GuassianSharpen", new GuassianSharpen(10) },
+            { "Hue-180", new Hue(180) },
+            { "Hue--180", new Hue(-180) }
         };
 
         [Theory]