refactor BoxBlur and GaussianBlur

src/ImageSharp/Processing/BoxBlurExtensions.cs

@@ -8,43 +8,37 @@ using SixLabors.Primitives;
 namespace SixLabors.ImageSharp.Processing
 {
     /// <summary>
-    /// Adds box blurring extensions to the <see cref="Image{TPixel}"/> type.
+    /// Adds box blurring extensions to the <see cref="Image"/> type.
     /// </summary>
     public static class BoxBlurExtensions
     {
         /// <summary>
         /// Applies a box blur to the image.
         /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The image this method extends.</param>
         /// <returns>The <see cref="Image{TPixel}"/>.</returns>
-        public static IImageProcessingContext<TPixel> BoxBlur<TPixel>(this IImageProcessingContext<TPixel> source)
-            where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new BoxBlurProcessor<TPixel>());
+        public static IImageProcessingContext BoxBlur(this IImageProcessingContext source)
+            => source.ApplyProcessor(new BoxBlurProcessor());
 
         /// <summary>
         /// Applies a box blur to the image.
         /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The image this method extends.</param>
         /// <param name="radius">The 'radius' value representing the size of the area to sample.</param>
         /// <returns>The <see cref="Image{TPixel}"/>.</returns>
-        public static IImageProcessingContext<TPixel> BoxBlur<TPixel>(this IImageProcessingContext<TPixel> source, int radius)
-            where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new BoxBlurProcessor<TPixel>(radius));
+        public static IImageProcessingContext BoxBlur(this IImageProcessingContext source, int radius)
+            => source.ApplyProcessor(new BoxBlurProcessor(radius));
 
         /// <summary>
         /// Applies a box blur to the image.
         /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The image this method extends.</param>
         /// <param name="radius">The 'radius' value representing the size of the area to sample.</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{TPixel}"/>.</returns>
-        public static IImageProcessingContext<TPixel> BoxBlur<TPixel>(this IImageProcessingContext<TPixel> source, int radius, Rectangle rectangle)
-            where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new BoxBlurProcessor<TPixel>(radius), rectangle);
+        public static IImageProcessingContext BoxBlur(this IImageProcessingContext source, int radius, Rectangle rectangle)
+            => source.ApplyProcessor(new BoxBlurProcessor(radius), rectangle);
     }
 }

src/ImageSharp/Processing/GaussianBlurExtensions.cs

@@ -8,43 +8,37 @@ using SixLabors.Primitives;
 namespace SixLabors.ImageSharp.Processing
 {
     /// <summary>
-    /// Adds Gaussian blurring extensions to the <see cref="Image{TPixel}"/> type.
+    /// Adds Gaussian blurring extensions to the <see cref="Image"/> type.
     /// </summary>
     public static class GaussianBlurExtensions
     {
         /// <summary>
         /// Applies a Gaussian blur to the image.
         /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The image this method extends.</param>
         /// <returns>The <see cref="Image{TPixel}"/>.</returns>
-        public static IImageProcessingContext<TPixel> GaussianBlur<TPixel>(this IImageProcessingContext<TPixel> source)
-            where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new GaussianBlurProcessor<TPixel>());
+        public static IImageProcessingContext GaussianBlur(this IImageProcessingContext source)
+            => source.ApplyProcessor(new GaussianBlurProcessor());
 
         /// <summary>
         /// Applies a Gaussian blur to the image.
         /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The image this method extends.</param>
         /// <param name="sigma">The 'sigma' value representing the weight of the blur.</param>
         /// <returns>The <see cref="Image{TPixel}"/>.</returns>
-        public static IImageProcessingContext<TPixel> GaussianBlur<TPixel>(this IImageProcessingContext<TPixel> source, float sigma)
-            where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new GaussianBlurProcessor<TPixel>(sigma));
+        public static IImageProcessingContext GaussianBlur(this IImageProcessingContext source, float sigma)
+            => source.ApplyProcessor(new GaussianBlurProcessor(sigma));
 
         /// <summary>
         /// Applies a Gaussian blur to the image.
         /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="source">The image this method extends.</param>
         /// <param name="sigma">The 'sigma' value representing the weight of the blur.</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{TPixel}"/>.</returns>
-        public static IImageProcessingContext<TPixel> GaussianBlur<TPixel>(this IImageProcessingContext<TPixel> source, float sigma, Rectangle rectangle)
-            where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new GaussianBlurProcessor<TPixel>(sigma), rectangle);
+        public static IImageProcessingContext GaussianBlur(this IImageProcessingContext source, float sigma, Rectangle rectangle)
+            => source.ApplyProcessor(new GaussianBlurProcessor(sigma), rectangle);
     }
 }

src/ImageSharp/Processing/Processors/Convolution/BoxBlurProcessor.cs

@@ -3,67 +3,48 @@
 
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Primitives;
-using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Convolution
 {
     /// <summary>
-    /// Applies box blur processing to the image.
+    /// Defines a box blur processor of a given Radius.
     /// </summary>
-    /// <typeparam name="TPixel">The pixel format.</typeparam>
-    internal class BoxBlurProcessor<TPixel> : ImageProcessor<TPixel>
-        where TPixel : struct, IPixel<TPixel>
+    public class BoxBlurProcessor : IImageProcessor
     {
         /// <summary>
-        /// The maximum size of the kernel in either direction.
+        /// The default radius used by the parameterless constructor.
         /// </summary>
-        private readonly int kernelSize;
+        public const int DefaultRadius = 7;
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="BoxBlurProcessor{TPixel}"/> class.
+        /// Initializes a new instance of the <see cref="BoxBlurProcessor"/> class.
         /// </summary>
         /// <param name="radius">
         /// The 'radius' value representing the size of the area to sample.
         /// </param>
-        public BoxBlurProcessor(int radius = 7)
+        public BoxBlurProcessor(int radius)
         {
             this.Radius = radius;
-            this.kernelSize = (radius * 2) + 1;
-            this.KernelX = this.CreateBoxKernel();
-            this.KernelY = this.KernelX.Transpose();
         }
 
         /// <summary>
-        /// Gets the Radius
+        /// Initializes a new instance of the <see cref="BoxBlurProcessor"/> class.
         /// </summary>
-        public int Radius { get; }
-
-        /// <summary>
-        /// Gets the horizontal gradient operator.
-        /// </summary>
-        public DenseMatrix<float> KernelX { get; }
+        public BoxBlurProcessor()
+            : this(DefaultRadius)
+        {
+        }
 
         /// <summary>
-        /// Gets the vertical gradient operator.
+        /// Gets the Radius.
         /// </summary>
-        public DenseMatrix<float> KernelY { get; }
-
-        /// <inheritdoc/>
-        protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration)
-            => new Convolution2PassProcessor<TPixel>(this.KernelX, this.KernelY, false).Apply(source, sourceRectangle, configuration);
+        public int Radius { get; }
 
-        /// <summary>
-        /// Create a 1 dimensional Box kernel.
-        /// </summary>
-        /// <returns>The <see cref="DenseMatrix{T}"/></returns>
-        private DenseMatrix<float> CreateBoxKernel()
+        /// <inheritdoc />
+        public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>()
+            where TPixel : struct, IPixel<TPixel>
         {
-            int size = this.kernelSize;
-            var kernel = new DenseMatrix<float>(size, 1);
-
-            kernel.Fill(1F / size);
-
-            return kernel;
+            return new BoxBlurProcessor<TPixel>(this);
         }
     }
 }

src/ImageSharp/Processing/Processors/Convolution/BoxBlurProcessor{TPixel}.cs

@@ -0,0 +1,64 @@
+// // Copyright (c) Six Labors and contributors.
+// // Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Primitives;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Processing.Processors.Convolution
+{
+    /// <summary>
+    /// Applies box blur processing to the image.
+    /// </summary>
+    /// <typeparam name="TPixel">The pixel format.</typeparam>
+    internal class BoxBlurProcessor<TPixel> : ImageProcessor<TPixel>
+        where TPixel : struct, IPixel<TPixel>
+    {
+        private readonly BoxBlurProcessor definition;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="BoxBlurProcessor{TPixel}"/> class.
+        /// </summary>
+        /// <param name="definition">The <see cref="BoxBlurProcessor"/> defining the processor parameters.</param>
+        public BoxBlurProcessor(BoxBlurProcessor definition)
+        {
+            this.definition = definition;
+            int kernelSize = (definition.Radius * 2) + 1;
+            this.KernelX = CreateBoxKernel(kernelSize);
+            this.KernelY = this.KernelX.Transpose();
+        }
+
+        /// <summary>
+        /// Gets the horizontal gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelX { get; }
+
+        /// <summary>
+        /// Gets the vertical gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelY { get; }
+
+
+        /// <inheritdoc/>
+        protected override void OnFrameApply(
+            ImageFrame<TPixel> source,
+            Rectangle sourceRectangle,
+            Configuration configuration) =>
+            new Convolution2PassProcessor<TPixel>(this.KernelX, this.KernelY, false).Apply(
+                source,
+                sourceRectangle,
+                configuration);
+
+        /// <summary>
+        /// Create a 1 dimensional Box kernel.
+        /// </summary>
+        /// <param name="kernelSize">The maximum size of the kernel in either direction.</param>
+        /// <returns>The <see cref="DenseMatrix{T}"/>.</returns>
+        private static DenseMatrix<float> CreateBoxKernel(int kernelSize)
+        {
+            var kernel = new DenseMatrix<float>(kernelSize, 1);
+            kernel.Fill(1F / kernelSize);
+            return kernel;
+        }
+    }
+}

src/ImageSharp/Processing/Processors/Convolution/GaussianBlurProcessor.cs

@@ -4,35 +4,38 @@
 using System;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Primitives;
-using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Convolution
 {
     /// <summary>
-    /// Applies Gaussian blur processing to the image.
+    /// Defines a gaussian blur processor with a (Sigma, Radius) pair.
     /// </summary>
-    /// <typeparam name="TPixel">The pixel format.</typeparam>
-    internal class GaussianBlurProcessor<TPixel> : ImageProcessor<TPixel>
-        where TPixel : struct, IPixel<TPixel>
+    public class GaussianBlurProcessor : IImageProcessor
     {
         /// <summary>
-        /// The maximum size of the kernel in either direction.
+        /// The default value for <see cref="Sigma"/>.
         /// </summary>
-        private readonly int kernelSize;
+        public const float DefaultSigma = 3f;
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="GaussianBlurProcessor{TPixel}"/> class.
+        /// Initializes a new instance of the <see cref="GaussianBlurProcessor"/> class.
+        /// </summary>
+        public GaussianBlurProcessor()
+            : this(DefaultSigma, CalculateDefaultRadius(DefaultSigma))
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GaussianBlurProcessor"/> class.
         /// </summary>
         /// <param name="sigma">The 'sigma' value representing the weight of the blur.</param>
-        public GaussianBlurProcessor(float sigma = 3F)
-            : this(sigma, (int)MathF.Ceiling(sigma * 3))
+        public GaussianBlurProcessor(float sigma)
+            : this(sigma, CalculateDefaultRadius(sigma))
         {
-            // Kernel radius is calculated using the minimum viable value.
-            // http://chemaguerra.com/gaussian-filter-radius/
         }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="GaussianBlurProcessor{TPixel}"/> class.
+        /// Initializes a new instance of the <see cref="GaussianBlurProcessor"/> class.
         /// </summary>
         /// <param name="radius">
         /// The 'radius' value representing the size of the area to sample.
@@ -43,7 +46,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="GaussianBlurProcessor{TPixel}"/> class.
+        /// Initializes a new instance of the <see cref="GaussianBlurProcessor"/> class.
         /// </summary>
         /// <param name="sigma">
         /// The 'sigma' value representing the weight of the blur.
@@ -54,10 +57,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// </param>
         public GaussianBlurProcessor(float sigma, int radius)
         {
-            this.kernelSize = (radius * 2) + 1;
             this.Sigma = sigma;
-            this.KernelX = this.CreateGaussianKernel();
-            this.KernelY = this.KernelX.Transpose();
+            this.Radius = radius;
         }
 
         /// <summary>
@@ -66,47 +67,24 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         public float Sigma { get; }
 
         /// <summary>
-        /// Gets the horizontal gradient operator.
-        /// </summary>
-        public DenseMatrix<float> KernelX { get; }
-
-        /// <summary>
-        /// Gets the vertical gradient operator.
+        /// Gets the radius defining the size of the area to sample.
         /// </summary>
-        public DenseMatrix<float> KernelY { get; }
+        public int Radius { get; }
 
-        /// <inheritdoc/>
-        protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration)
-            => new Convolution2PassProcessor<TPixel>(this.KernelX, this.KernelY, false).Apply(source, sourceRectangle, configuration);
+        /// <inheritdoc />
+        public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>()
+            where TPixel : struct, IPixel<TPixel>
+        {
+            return new GaussianBlurProcessor<TPixel>(this);
+        }
 
         /// <summary>
-        /// Create a 1 dimensional Gaussian kernel using the Gaussian G(x) function
+        /// Kernel radius is calculated using the minimum viable value.
+        /// <see cref="http://chemaguerra.com/gaussian-filter-radius/"/>.
         /// </summary>
-        /// <returns>The <see cref="DenseMatrix{T}"/></returns>
-        private DenseMatrix<float> CreateGaussianKernel()
+        private static int CalculateDefaultRadius(float sigma)
         {
-            int size = this.kernelSize;
-            float weight = this.Sigma;
-            var kernel = new DenseMatrix<float>(size, 1);
-
-            float sum = 0F;
-            float midpoint = (size - 1) / 2F;
-
-            for (int i = 0; i < size; i++)
-            {
-                float x = i - midpoint;
-                float gx = ImageMaths.Gaussian(x, weight);
-                sum += gx;
-                kernel[0, i] = gx;
-            }
-
-            // Normalize kernel so that the sum of all weights equals 1
-            for (int i = 0; i < size; i++)
-            {
-                kernel[0, i] /= sum;
-            }
-
-            return kernel;
+            return (int)MathF.Ceiling(sigma * 3);
         }
     }
 }

src/ImageSharp/Processing/Processors/Convolution/GaussianBlurProcessor{TPixel}.cs

@@ -0,0 +1,79 @@
+// // Copyright (c) Six Labors and contributors.
+// // Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Primitives;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Processing.Processors.Convolution
+{
+    /// <summary>
+    /// Applies Gaussian blur processing to an image.
+    /// </summary>
+    /// <typeparam name="TPixel">The pixel format.</typeparam>
+    internal class GaussianBlurProcessor<TPixel> : ImageProcessor<TPixel>
+        where TPixel : struct, IPixel<TPixel>
+    {
+        private readonly GaussianBlurProcessor definition;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GaussianBlurProcessor{TPixel}"/> class.
+        /// </summary>
+        /// <param name="definition">The <see cref="GaussianBlurProcessor"/> defining the processor parameters.</param>
+        public GaussianBlurProcessor(GaussianBlurProcessor definition)
+        {
+            this.definition = definition;
+            int kernelSize = (definition.Radius * 2) + 1;
+            this.KernelX = CreateGaussianKernel(kernelSize, definition.Sigma);
+            this.KernelY = this.KernelX.Transpose();
+        }
+
+        /// <summary>
+        /// Gets the horizontal gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelX { get; }
+
+        /// <summary>
+        /// Gets the vertical gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelY { get; }
+
+        /// <inheritdoc/>
+        protected override void OnFrameApply(
+            ImageFrame<TPixel> source,
+            Rectangle sourceRectangle,
+            Configuration configuration) =>
+            new Convolution2PassProcessor<TPixel>(this.KernelX, this.KernelY, false).Apply(
+                source,
+                sourceRectangle,
+                configuration);
+
+        /// <summary>
+        /// Create a 1 dimensional Gaussian kernel using the Gaussian G(x) function
+        /// </summary>
+        /// <returns>The <see cref="DenseMatrix{T}"/></returns>
+        private static DenseMatrix<float> CreateGaussianKernel(int size, float weight)
+        {
+            var kernel = new DenseMatrix<float>(size, 1);
+
+            float sum = 0F;
+            float midpoint = (size - 1) / 2F;
+
+            for (int i = 0; i < size; i++)
+            {
+                float x = i - midpoint;
+                float gx = ImageMaths.Gaussian(x, weight);
+                sum += gx;
+                kernel[0, i] = gx;
+            }
+
+            // Normalize kernel so that the sum of all weights equals 1
+            for (int i = 0; i < size; i++)
+            {
+                kernel[0, i] /= sum;
+            }
+
+            return kernel;
+        }
+    }
+}

tests/ImageSharp.Tests/Processing/Convolution/BoxBlurTest.cs

@@ -14,7 +14,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
         public void BoxBlur_BoxBlurProcessorDefaultsSet()
         {
             this.operations.BoxBlur();
-            var processor = this.Verify<BoxBlurProcessor<Rgba32>>();
+            var processor = this.Verify<BoxBlurProcessor>();
 
             Assert.Equal(7, processor.Radius);
         }
@@ -23,7 +23,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
         public void BoxBlur_amount_BoxBlurProcessorDefaultsSet()
         {
             this.operations.BoxBlur(34);
-            var processor = this.Verify<BoxBlurProcessor<Rgba32>>();
+            var processor = this.Verify<BoxBlurProcessor>();
 
             Assert.Equal(34, processor.Radius);
         }
@@ -32,7 +32,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
         public void BoxBlur_amount_rect_BoxBlurProcessorDefaultsSet()
         {
             this.operations.BoxBlur(5, this.rect);
-            var processor = this.Verify<BoxBlurProcessor<Rgba32>>(this.rect);
+            var processor = this.Verify<BoxBlurProcessor>(this.rect);
 
             Assert.Equal(5, processor.Radius);
         }

tests/ImageSharp.Tests/Processing/Convolution/GaussianBlurTest.cs

@@ -14,7 +14,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
         public void GaussianBlur_GaussianBlurProcessorDefaultsSet()
         {
             this.operations.GaussianBlur();
-            var processor = this.Verify<GaussianBlurProcessor<Rgba32>>();
+            var processor = this.Verify<GaussianBlurProcessor>();
 
             Assert.Equal(3f, processor.Sigma);
         }
@@ -23,7 +23,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
         public void GaussianBlur_amount_GaussianBlurProcessorDefaultsSet()
         {
             this.operations.GaussianBlur(0.2f);
-            var processor = this.Verify<GaussianBlurProcessor<Rgba32>>();
+            var processor = this.Verify<GaussianBlurProcessor>();
 
             Assert.Equal(.2f, processor.Sigma);
         }
@@ -32,7 +32,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
         public void GaussianBlur_amount_rect_GaussianBlurProcessorDefaultsSet()
         {
             this.operations.GaussianBlur(0.6f, this.rect);
-            var processor = this.Verify<GaussianBlurProcessor<Rgba32>>(this.rect);
+            var processor = this.Verify<GaussianBlurProcessor>(this.rect);
 
             Assert.Equal(.6f, processor.Sigma);
         }