Adding some resamplers

Former-commit-id: 173de39596036ccb0970ae195d47874cb5610db6
Former-commit-id: 156b60bd82d6e2d49c0733aa5954206417d63501
Former-commit-id: 6639ef8d33a006707c408193122d001189eec15d

src/ImageProcessor/Common/Helpers/ImageMaths.cs

@@ -12,6 +12,41 @@ namespace ImageProcessor
     /// </summary>
     internal static class ImageMaths
     {
+        /// <summary>
+        /// Returns the result of a B-C filter against the given value.
+        /// <see href="http://www.imagemagick.org/Usage/filter/#cubic_bc"/>
+        /// </summary>
+        /// <param name="x">The value to process.</param>
+        /// <param name="b">The B-Spline curve variable.</param>
+        /// <param name="c">The Cardinal curve variable.</param>
+        /// <returns>
+        /// The <see cref="double"/>.
+        /// </returns>
+        public static double GetBcValue(double x, double b, double c)
+        {
+            double temp;
+
+            if (x < 0)
+            {
+                x = -x;
+            }
+
+            temp = x * x;
+            if (x < 1)
+            {
+                x = ((12 - (9 * b) - (6 * c)) * (x * temp)) + ((-18 + (12 * b) + (6 * c)) * temp) + (6 - (2 * b));
+                return x / 6;
+            }
+
+            if (x < 2)
+            {
+                x = ((-b - (6 * c)) * (x * temp)) + (((6 * b) + (30 * c)) * temp) + (((-12 * b) - (48 * c)) * x) + ((8 * b) + (24 * c));
+                return x / 6;
+            }
+
+            return 0;
+        }
+
         /// <summary>
         /// Gets the result of a sine cardinal function for the given value.
         /// </summary>

src/ImageProcessor/ImageProcessor.csproj

@@ -181,10 +181,20 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Numerics\Rectangle.cs" />
     <Compile Include="Numerics\Size.cs" />
-    <Compile Include="Samplers\Lanczos5Resampler.cs" />
+    <Compile Include="Samplers\Resamplers\WelchResampler.cs" />
-    <Compile Include="Samplers\BicubicResampler.cs" />
+    <Compile Include="Samplers\Resamplers\CatmullRomResampler.cs" />
+    <Compile Include="Samplers\Resamplers\RobidouxSoftResampler.cs" />
+    <Compile Include="Samplers\Resamplers\RobidouxSharpResampler.cs" />
+    <Compile Include="Samplers\Resamplers\RobidouxResampler.cs" />
+    <Compile Include="Samplers\Resamplers\SplineResampler.cs" />
+    <Compile Include="Samplers\Resamplers\HermiteResampler.cs" />
+    <Compile Include="Samplers\Resamplers\MitchellNetravaliResampler.cs" />
+    <Compile Include="Samplers\Resamplers\TriangleResampler.cs" />
+    <Compile Include="Samplers\Resamplers\BoxResampler.cs" />
+    <Compile Include="Samplers\Resamplers\Lanczos3Resampler.cs" />
+    <Compile Include="Samplers\Resamplers\BicubicResampler.cs" />
     <Compile Include="Samplers\ImageSampleExtensions.cs" />
-    <Compile Include="Samplers\IResampler.cs" />
+    <Compile Include="Samplers\Resamplers\IResampler.cs" />
     <Compile Include="Samplers\Resize.cs" />
   </ItemGroup>
   <ItemGroup>
@@ -197,7 +207,6 @@
     <None Include="Formats\Gif\README.md" />
     <None Include="Formats\Jpg\README.md" />
     <None Include="packages.config" />
-    <AdditionalFiles Include="stylecop.json" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Formats\Bmp\README.md" />

src/ImageProcessor/ImageProcessor.csproj.DotSettings

@@ -12,4 +12,5 @@
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=formats_005Cjpg/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=formats_005Cjpg_005Clibjpeg/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=formats_005Cpng/@EntryIndexedValue">True</s:Boolean>
-	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=numerics/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=numerics/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=samplers_005Cresamplers/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

src/ImageProcessor/Samplers/BicubicResampler.cs → src/ImageProcessor/Samplers/Resamplers/BicubicResampler.cs

@@ -12,7 +12,7 @@ namespace ImageProcessor.Samplers
     public class BicubicResampler : IResampler
     {
         /// <inheritdoc/>
-        public double Radius => 4;
+        public double Radius => 2;
 
         /// <inheritdoc/>
         public double GetValue(double x)

src/ImageProcessor/Samplers/Resamplers/BoxResampler.cs

@@ -0,0 +1,32 @@
+// <copyright file="BoxResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the box (nearest neighbour) algorithm.
+    /// </summary>
+    public class BoxResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 0.5;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            if (x < 0)
+            {
+                x = -x;
+            }
+
+            if (x <= 0.5)
+            {
+                return 1;
+            }
+
+            return 0;
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/CatmullRomResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="CatmullRomResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the Catmull-Rom algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/#cubic_bc"/>
+    /// </summary>
+    public class CatmullRomResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 0;
+            const double C = 1 / 2d;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/HermiteResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="HermiteResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the hermite algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/#cubic_bc"/>
+    /// </summary>
+    public class HermiteResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 0;
+            const double C = 0;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Lanczos5Resampler.cs → src/ImageProcessor/Samplers/Resamplers/Lanczos3Resampler.cs

@@ -1,4 +1,4 @@
-// <copyright file="BicubicResampler.cs" company="James South">
+// <copyright file="Lanczos3Resampler.cs" company="James South">
 // Copyright © James South and contributors.
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
@@ -9,10 +9,10 @@ namespace ImageProcessor.Samplers
     /// The function implements the Lanczos kernel algorithm as described on
     /// <see href="https://en.wikipedia.org/wiki/Lanczos_resampling#Algorithm">Wikipedia</see>
     /// </summary>
-    public class Lanczos5Resampler : IResampler
+    public class Lanczos3Resampler : IResampler
     {
         /// <inheritdoc/>
-        public double Radius => 5;
+        public double Radius => 3;
 
         /// <inheritdoc/>
         public double GetValue(double x)

src/ImageProcessor/Samplers/Resamplers/MitchellNetravaliResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="MitchellResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the mitchell algorithm as described on
+    /// <see href="https://de.wikipedia.org/wiki/Mitchell-Netravali-Filter">Wikipedia</see>
+    /// </summary>
+    public class MitchellNetravaliResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 1 / 3d;
+            const double C = 1 / 3d;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/RobidouxResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="RobidouxResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the Robidoux algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/#robidoux"/>
+    /// </summary>
+    public class RobidouxResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 0.3782;
+            const double C = 0.3109;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/RobidouxSharpResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="RobidouxSharpResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the Robidoux Sharp algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/#robidoux"/>
+    /// </summary>
+    public class RobidouxSharpResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 0.2620;
+            const double C = 0.3690;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/RobidouxSoftResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="RobidouxSoftResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the Robidoux Soft algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/#robidoux"/>
+    /// </summary>
+    public class RobidouxSoftResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 0.6796;
+            const double C = 0.1602;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/SplineResampler.cs

@@ -0,0 +1,26 @@
+// <copyright file="SplineResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the spline algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/#cubic_bc"/>
+    /// </summary>
+    public class SplineResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 2;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            const double B = 1;
+            const double C = 0;
+
+            return ImageMaths.GetBcValue(x, B, C);
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/TriangleResampler.cs

@@ -0,0 +1,32 @@
+// <copyright file="TriangleResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the triangle (bilinear) algorithm.
+    /// </summary>
+    public class TriangleResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 1;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            if (x < 0)
+            {
+                x = -x;
+            }
+
+            if (x < 1)
+            {
+                return 1 - x;
+            }
+
+            return 0;
+        }
+    }
+}

src/ImageProcessor/Samplers/Resamplers/WelchResampler.cs

@@ -0,0 +1,33 @@
+// <copyright file="WelchResampler.cs" company="James South">
+// Copyright © James South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessor.Samplers
+{
+    /// <summary>
+    /// The function implements the welch algorithm.
+    /// <see href="http://www.imagemagick.org/Usage/filter/"/>
+    /// </summary>
+    public class WelchResampler : IResampler
+    {
+        /// <inheritdoc/>
+        public double Radius => 3;
+
+        /// <inheritdoc/>
+        public double GetValue(double x)
+        {
+            if (x < 0)
+            {
+                x = -x;
+            }
+
+            if (x < 3)
+            {
+                return ImageMaths.SinC(x) * (1.0 - (x * x / 9.0));
+            }
+
+            return 0;
+        }
+    }
+}

src/ImageProcessor/Samplers/Resize.cs

@@ -12,6 +12,11 @@ namespace ImageProcessor.Samplers
     /// </summary>
     public class Resize : ParallelImageProcessor
     {
+        /// <summary>
+        /// The epsilon for comparing floating point numbers.
+        /// </summary>
+        private const float Epsilon = 0.0001f;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Resize"/> class.
         /// </summary>
@@ -78,11 +83,16 @@ namespace ImageProcessor.Samplers
                             double b = 0;
                             double a = 0;
 
-                            for (int yy = left; yy < right; yy++)
+                            for (int yy = left; yy <= right; yy++)
                             {
                                 // Get Y cooefficient
                                 double kernel1 = this.Sampler.GetValue(dy - yy);
 
+                                if (Math.Abs(kernel1) < Epsilon)
+                                {
+                                    continue;
+                                }
+
                                 int originY2 = originY1 + yy;
                                 if (originY2 < 0)
                                 {
@@ -94,11 +104,16 @@ namespace ImageProcessor.Samplers
                                     originY2 = maxHeight;
                                 }
 
-                                for (int xx = left; xx < right; xx++)
+                                for (int xx = left; xx <= right; xx++)
                                 {
                                     // Get X cooefficient
                                     double kernel2 = kernel1 * this.Sampler.GetValue(xx - dx);
 
+                                    if (Math.Abs(kernel2) < Epsilon)
+                                    {
+                                        continue;
+                                    }
+
                                     int originX2 = originX1 + xx;
                                     if (originX2 < 0)
                                     {

tests/ImageProcessor.Tests/Processors/Samplers/SamplerTests.cs

@@ -14,7 +14,16 @@ namespace ImageProcessor.Tests
             new TheoryData<string, IResampler>
             {
                 { "Bicubic", new BicubicResampler() },
-                //{ "Lanczos3", new Lanczos5Resampler() }
+                { "Bilinear", new TriangleResampler() },
+                { "NearestNeighbour", new BoxResampler() },
+                { "Lanczos3", new Lanczos3Resampler() },
+                { "MitchellNetravali", new MitchellNetravaliResampler() },
+                { "Hermite", new HermiteResampler() },
+                { "Spline", new SplineResampler() },
+                { "Robidoux", new RobidouxResampler() },
+                { "RobidouxSharp", new RobidouxSharpResampler() },
+                { "RobidouxSoft", new RobidouxSoftResampler() },
+                { "Welch", new WelchResampler() }
             };
 
         [Theory]
@@ -52,7 +61,7 @@ namespace ImageProcessor.Tests
         [InlineData(2, 0)]
         public static void Lanczos3WindowOscillatesCorrectly(double x, double expected)
         {
-            Lanczos5Resampler sampler = new Lanczos5Resampler();
+            Lanczos3Resampler sampler = new Lanczos3Resampler();
             double result = sampler.GetValue(x);
 
             Assert.Equal(result, expected);