Begin Gaussian filters

Former-commit-id: 9ba003b66ca7eac43c5012ebc44d284ef2373b98
Former-commit-id: 3ac80f0e2d15bea7bb33e5bcbb3285cd1b828a7c
Former-commit-id: 4a36925ddffbbf62a4e6a33939730a91bc294e14

src/ImageProcessor/Filters/Convolution/GuassianBlur.cs

@@ -0,0 +1,116 @@
+namespace ImageProcessor.Filters.Convolution
+{
+    using System;
+    using System.Runtime.CompilerServices;
+
+    public class GuassianBlur : ConvolutionFilter
+    {
+        private int kernelSize;
+
+        private float standardDeviation;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GuassianBlur"/> class.
+        /// </summary>
+        /// <param name="size">
+        /// The size.
+        /// </param>
+        /// <param name="standardDeviation">
+        /// The standard deviation 'sigma' value for calculating Gaussian curves.
+        /// </param>
+        public GuassianBlur(int size, float standardDeviation)
+        {
+            this.kernelSize = size;
+            this.standardDeviation = standardDeviation;
+        }
+
+        public override float[,] KernelX { get; }
+
+        /// <summary>
+        /// Create a 2 dimensional Gaussian kernel using the Gaussian G(x y) function for 
+        /// blurring images.
+        /// </summary>
+        /// <param name="kernelSize">Kernel Size</param>
+        /// <returns>A Gaussian Kernel with the given size.</returns>
+        private float[,] CreateGuassianBlurFilter()
+        {
+            // Create kernel
+            int size = this.kernelSize;
+            float[,] kernel = this.CreateGaussianKernel2D(size);
+            float min = kernel[0, 0];
+
+            // Convert to integer blurring kernel. First of all the integer kernel is calculated from Kernel2D
+            // by dividing all elements by the element with the smallest value.
+            float[,] intKernel = new float[size, size];
+            int divider = 0;
+
+            for (int i = 0; i < size; i++)
+            {
+                for (int j = 0; j < size; j++)
+                {
+                    float v = kernel[i, j] / min;
+
+                    if (v > ushort.MaxValue)
+                    {
+                        v = ushort.MaxValue;
+                    }
+
+                    intKernel[i, j] = (int)v;
+
+                    // Collect the divider
+                    divider += (int)intKernel[i, j];
+                }
+            }
+
+            // Update filter
+            //this.Divider = divider;
+            return intKernel;
+        }
+
+        /// <summary>
+        /// Create a 2 dimensional Gaussian kernel using the Gaussian G(x y) function
+        /// </summary>
+        /// <param name="kernelSize">Kernel Size</param>
+        /// <returns>A Gaussian Kernel with the given size and deviation.</returns>
+        public float[,] CreateGaussianKernel2D(int kernelSize)
+        {
+            float[,] kernel = new float[kernelSize, kernelSize];
+
+            int midpoint = kernelSize / 2;
+
+            for (int i = 0; i < kernelSize; i++)
+            {
+                int x = i - midpoint;
+
+                for (int j = 0; j < kernelSize; j++)
+                {
+                    int y = j - midpoint;
+                    float gxy = this.Gaussian2D(x, y);
+                    kernel[i, j] = gxy;
+                }
+            }
+
+            return kernel;
+        }
+
+        /// <summary>
+        /// Implementation of 2D Gaussian G(x) function
+        /// </summary>
+        /// <param name="x">The x provided to G(x y)</param>
+        /// <param name="y">The y provided to G(x y)</param>
+        /// <returns>The Gaussian G(x y)</returns>
+        private float Gaussian2D(float x, float y)
+        {
+            const float Numerator = 1.0f;
+            float denominator = (float)((2 * Math.PI) * Math.Pow(this.standardDeviation, 2));
+
+            float exponentNumerator = (-x * x) + (-y * y);
+            float exponentDenominator = (float)(2 * Math.Pow(this.standardDeviation, 2));
+
+            float left = Numerator / denominator;
+            float right = (float)Math.Exp(exponentNumerator / exponentDenominator);
+
+            return left * right;
+        }
+    }
+}

src/ImageProcessor/ImageProcessor.csproj

@@ -49,6 +49,7 @@
     <Compile Include="Common\Helpers\ImageMaths.cs" />
     <Compile Include="Common\Helpers\PixelOperations.cs" />
     <Compile Include="Filters\Blend.cs" />
+    <Compile Include="Filters\ColorMatrix\IColorMatrixFilter.cs" />
     <Compile Include="Filters\Convolution\Convolution2DFilter.cs" />
     <Compile Include="Filters\ColorMatrix\ColorMatrixFilter.cs" />
     <Compile Include="Filters\ColorMatrix\Kodachrome.cs" />
@@ -64,6 +65,7 @@
     <Compile Include="Filters\Convolution\EdgeDetection\Kirsch.cs" />
     <Compile Include="Filters\Convolution\EdgeDetection\Kayyali.cs" />
     <Compile Include="Filters\Convolution\EdgeDetection\Sobel.cs" />
+    <Compile Include="Filters\Convolution\GuassianBlur.cs" />
     <Compile Include="Filters\Invert.cs" />
     <Compile Include="Filters\Alpha.cs" />
     <Compile Include="Filters\ColorMatrix\GreyscaleBt601.cs" />