Refactoring entropy crop

Former-commit-id: f6d222bdb990035f155162523ac8d2eaab7e57e9
Former-commit-id: 2cc168df666dc13196df282de960242e2db5785a

src/ImageProcessor.Playground/Program.cs

@@ -50,7 +50,7 @@ namespace ImageProcessor.PlayGround
             }
 
             Image mask = Image.FromFile(Path.Combine(resolvedPath, "mask.png"));
-            IEnumerable<FileInfo> files = GetFilesByExtensions(di, ".jpg");
+            IEnumerable<FileInfo> files = GetFilesByExtensions(di, ".png");
             //IEnumerable<FileInfo> files = GetFilesByExtensions(di, ".gif", ".webp", ".bmp", ".jpg", ".png", ".tif");
 
             foreach (FileInfo fileInfo in files)
@@ -85,9 +85,9 @@ namespace ImageProcessor.PlayGround
                             //.Resize(layer)
                             //.DetectEdges(new SobelEdgeFilter(), false)
                             //.DetectEdges(new LaplacianOfGaussianEdgeFilter())
-                            //.EntropyCrop()
+                            .EntropyCrop()
                             //.Filter(MatrixFilters.Invert)
-                            .Filter(MatrixFilters.Comic)
+                            //.Filter(MatrixFilters.Comic)
                             //.Filter(MatrixFilters.HiSatch)
                             //.Pixelate(8)
                             //.GaussianSharpen(10)

src/ImageProcessor/ImageProcessor.csproj

@@ -133,6 +133,7 @@
     <Compile Include="Configuration\NativeMethods.cs" />
     <Compile Include="Imaging\Colors\HslaColor.cs" />
     <Compile Include="Imaging\Colors\RgbaColor.cs" />
+    <Compile Include="Imaging\Colors\RgbaComponent.cs" />
     <Compile Include="Imaging\Colors\YCbCrColor.cs" />
     <Compile Include="Imaging\Filters\Artistic\OilPaintingFilter.cs" />
     <Compile Include="Imaging\Filters\EdgeDetection\ConvolutionFilter.cs" />

src/ImageProcessor/Imaging/Colors/RgbaComponent.cs

@@ -0,0 +1,38 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="RgbaComponent.cs" company="James South">
+//   Copyright (c) James South.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Enumerates the RGBA (red, green, blue, alpha) color components.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Imaging.Colors
+{
+    /// <summary>
+    /// Enumerates the RGBA (red, green, blue, alpha) color components.
+    /// </summary>
+    public enum RgbaComponent
+    {
+        /// <summary>
+        /// The blue component.
+        /// </summary>
+        B = 0,
+
+        /// <summary>
+        /// The green component.
+        /// </summary>
+        G = 1,
+
+        /// <summary>
+        /// The red component.
+        /// </summary>
+        R = 2,
+
+        /// <summary>
+        /// The alpha component.
+        /// </summary>
+        A = 3
+    }
+}

src/ImageProcessor/Imaging/Helpers/ImageMaths.cs

@@ -10,8 +10,11 @@
 
 namespace ImageProcessor.Imaging.Helpers
 {
+    using System;
     using System.Drawing;
 
+    using ImageProcessor.Imaging.Colors;
+
     /// <summary>
     /// Provides reusable mathematical methods to apply to images.
     /// </summary>
@@ -34,6 +37,123 @@ namespace ImageProcessor.Imaging.Helpers
             return new Rectangle(topLeft.X, topLeft.Y, bottomRight.X - topLeft.X, bottomRight.Y - topLeft.Y);
         }
 
+        /// <summary>
+        /// Finds the bounding rectangle based on the first instance of any color component other
+        /// than the given one.
+        /// </summary>
+        /// <param name="bitmap">
+        /// The <see cref="Image"/> to search within.
+        /// </param>
+        /// <param name="componentValue">
+        /// The color component value to remove.
+        /// </param>
+        /// <param name="channel">
+        /// The <see cref="RgbaComponent"/> channel to test against.
+        /// </param>
+        /// <returns>
+        /// The <see cref="Rectangle"/>.
+        /// </returns>
+        public static Rectangle GetFilteredBoundingRectangle(Image bitmap, byte componentValue, RgbaComponent channel = RgbaComponent.B)
+        {
+            int width = bitmap.Width;
+            int height = bitmap.Height;
+            Point topLeft = new Point();
+            Point bottomRight = new Point();
+
+            Func<FastBitmap, int, int, byte, bool> delegateFunc;
+
+            // Determine which channel to check against
+            switch (channel)
+            {
+                case RgbaComponent.R:
+                    delegateFunc = (fastBitmap, x, y, b) => fastBitmap.GetPixel(x, y).R != b;
+                    break;
+                case RgbaComponent.G:
+                    delegateFunc = (fastBitmap, x, y, b) => fastBitmap.GetPixel(x, y).G != b;
+                    break;
+                case RgbaComponent.A:
+                    delegateFunc = (fastBitmap, x, y, b) => fastBitmap.GetPixel(x, y).A != b;
+                    break;
+                default:
+                    delegateFunc = (fastBitmap, x, y, b) => fastBitmap.GetPixel(x, y).B != b;
+                    break;
+            }
+
+            Func<FastBitmap, int> getMinY = fastBitmap =>
+            {
+                for (int y = 0; y < height; y++)
+                {
+                    for (int x = 0; x < width; x++)
+                    {
+                        if (delegateFunc(fastBitmap, x, y, componentValue))
+                        {
+                            return y;
+                        }
+                    }
+                }
+
+                return 0;
+            };
+
+            Func<FastBitmap, int> getMaxY = fastBitmap =>
+            {
+                for (int y = height - 1; y > -1; y--)
+                {
+                    for (int x = 0; x < width; x++)
+                    {
+                        if (delegateFunc(fastBitmap, x, y, componentValue))
+                        {
+                            return y;
+                        }
+                    }
+                }
+
+                return height;
+            };
+
+            Func<FastBitmap, int> getMinX = fastBitmap =>
+            {
+                for (int x = 0; x < width; x++)
+                {
+                    for (int y = 0; y < height; y++)
+                    {
+                        if (delegateFunc(fastBitmap, x, y, componentValue))
+                        {
+                            return x;
+                        }
+                    }
+                }
+
+                return 0;
+            };
+
+            Func<FastBitmap, int> getMaxX = fastBitmap =>
+            {
+                for (int x = width - 1; x > -1; x--)
+                {
+                    for (int y = 0; y < height; y++)
+                    {
+                        if (delegateFunc(fastBitmap, x, y, componentValue))
+                        {
+                            return x;
+                        }
+                    }
+                }
+
+                return height;
+            };
+
+            using (FastBitmap fastBitmap = new FastBitmap(bitmap))
+            {
+                topLeft.Y = getMinY(fastBitmap) + 1;
+                topLeft.X = getMinX(fastBitmap) + 1;
+                bottomRight.Y = getMaxY(fastBitmap);
+                bottomRight.X = getMaxX(fastBitmap);
+            }
+
+            return ImageMaths.GetBoundingRectangle(topLeft, bottomRight);
+        }
+
         /// <summary>
         /// Gets a <see cref="Rectangle"/> representing the child centered relative to the parent.
         /// </summary>

src/ImageProcessor/Imaging/PixelData.cs

@@ -10,29 +10,36 @@
 
 namespace ImageProcessor.Imaging
 {
+    using System.Runtime.InteropServices;
+
     /// <summary>
     /// Contains the component parts that make up a single pixel.
     /// </summary>
+    [StructLayout(LayoutKind.Explicit)]
     public struct PixelData
     {
         /// <summary>
         /// The blue component.
         /// </summary>
+        [FieldOffset(0)]
         public byte B;
 
         /// <summary>
         /// The green component.
         /// </summary>
+        [FieldOffset(1)]
         public byte G;
 
         /// <summary>
         /// The red component.
         /// </summary>
+        [FieldOffset(2)]
         public byte R;
 
         /// <summary>
         /// The alpha component.
         /// </summary>
+        [FieldOffset(3)]
         public byte A;
 
         /// <summary>

src/ImageProcessor/Processors/EntropyCrop.cs

@@ -12,9 +12,9 @@ namespace ImageProcessor.Processors
     using System.Drawing;
 
     using ImageProcessor.Common.Exceptions;
-    using ImageProcessor.Imaging;
     using ImageProcessor.Imaging.Filters.Binarization;
     using ImageProcessor.Imaging.Filters.EdgeDetection;
+    using ImageProcessor.Imaging.Helpers;
 
     /// <summary>
     /// Performs a crop on an image to the area of greatest entropy.
@@ -61,8 +61,9 @@ namespace ImageProcessor.Processors
                 // Detect the edges then strip out middle shades.
                 grey = new ConvolutionFilter(new SobelEdgeFilter(), true).Process2DFilter(image);
                 grey = new BinaryThreshold(threshold).ProcessFilter(grey);
-                
-                Rectangle rectangle = this.FindBoundingBox(grey, 0);
+
+                // Search for the first white pixels
+                Rectangle rectangle = ImageMaths.GetFilteredBoundingRectangle(grey, 0);
 
                 newImage = new Bitmap(rectangle.Width, rectangle.Height);
                 using (Graphics graphics = Graphics.FromImage(newImage))
@@ -99,102 +100,5 @@ namespace ImageProcessor.Processors
 
             return image;
         }
-
-        /// <summary>
-        /// Finds the bounding rectangle based on the first instance of any color component other
-        /// than the given one.
-        /// </summary>
-        /// <param name="bitmap">
-        /// The bitmap.
-        /// </param>
-        /// <param name="componentToRemove">
-        /// The color component to remove.
-        /// </param>
-        /// <returns>
-        /// The <see cref="Rectangle"/>.
-        /// </returns>
-        private Rectangle FindBoundingBox(Bitmap bitmap, byte componentToRemove)
-        {
-            int width = bitmap.Width;
-            int height = bitmap.Height;
-            int startX;
-            int startY;
-            int stopX;
-            int stopY;
-
-            Func<FastBitmap, int> getMinY = fastBitmap =>
-            {
-                for (int y = 0; y < height; y++)
-                {
-                    for (int x = 0; x < width; x++)
-                    {
-                        if (fastBitmap.GetPixel(x, y).B != componentToRemove)
-                        {
-                            return y;
-                        }
-                    }
-                }
-
-                return 0;
-            };
-
-            Func<FastBitmap, int> getMaxY = fastBitmap =>
-            {
-                for (int y = height - 1; y > -1; y--)
-                {
-                    for (int x = 0; x < width; x++)
-                    {
-                        if (fastBitmap.GetPixel(x, y).B != componentToRemove)
-                        {
-                            return y;
-                        }
-                    }
-                }
-
-                return height;
-            };
-
-            Func<FastBitmap, int> getMinX = fastBitmap =>
-            {
-                for (int x = 0; x < width; x++)
-                {
-                    for (int y = 0; y < height; y++)
-                    {
-                        if (fastBitmap.GetPixel(x, y).B != componentToRemove)
-                        {
-                            return x;
-                        }
-                    }
-                }
-
-                return 0;
-            };
-
-            Func<FastBitmap, int> getMaxX = fastBitmap =>
-            {
-                for (int x = width - 1; x > -1; x--)
-                {
-                    for (int y = 0; y < height; y++)
-                    {
-                        if (fastBitmap.GetPixel(x, y).B != componentToRemove)
-                        {
-                            return x;
-                        }
-                    }
-                }
-
-                return height;
-            };
-
-            using (FastBitmap fastBitmap = new FastBitmap(bitmap))
-            {
-                startY = getMinY(fastBitmap);
-                stopY = getMaxY(fastBitmap);
-                startX = getMinX(fastBitmap);
-                stopX = getMaxX(fastBitmap);
-            }
-
-            return new Rectangle(startX + 1, startY + 1, stopX - (startX + 1), stopY - (startY + 1));
-        }
     }
 }