Adding some helpers for Mask

Former-commit-id: d969389a44ba0315b1aae749ac56415a836ecfdd
Former-commit-id: 8dcbde421d92d9f54e4f3510ae7b9196608cfd69

src/ImageProcessor/ImageProcessor.csproj

@@ -155,6 +155,7 @@
     <Compile Include="Common\Exceptions\ImageFormatException.cs" />
     <Compile Include="ImageFactory.cs" />
     <Compile Include="Imaging\AnchorPosition.cs" />
+    <Compile Include="Imaging\Helpers\ImageMaths.cs" />
     <Compile Include="Imaging\MetaData\ExifPropertyTagType.cs" />
     <Compile Include="Imaging\Convolution.cs" />
     <Compile Include="Imaging\CropLayer.cs" />

src/ImageProcessor/Imaging/Helpers/ImageMaths.cs

@@ -0,0 +1,62 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="ImageMaths.cs" company="James South">
+//   Copyright (c) James South.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   Provides reusable mathematical methods to apply to images.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Imaging.Helpers
+{
+    using System.Drawing;
+
+    /// <summary>
+    /// Provides reusable mathematical methods to apply to images.
+    /// </summary>
+    public class ImageMaths
+    {
+        /// <summary>
+        /// Gets the bounding <see cref="Rectangle"/> from the given points.
+        /// </summary>
+        /// <param name="topLeft">
+        /// The <see cref="Point"/> designating the top left position.
+        /// </param>
+        /// <param name="bottomRight">
+        /// The <see cref="Point"/> designating the bottom right position.
+        /// </param>
+        /// <returns>
+        /// The bounding <see cref="Rectangle"/>.
+        /// </returns>
+        public Rectangle GetBoundingRectangle(Point topLeft, Point bottomRight)
+        {
+            return new Rectangle(topLeft.X, topLeft.Y, bottomRight.X - topLeft.X, bottomRight.Y - topLeft.Y);
+        }
+
+        /// <summary>
+        /// Gets a <see cref="Rectangle"/> centered within it's parent.
+        /// </summary>
+        /// <param name="parent">
+        /// The parent <see cref="Rectangle"/>.
+        /// </param>
+        /// <param name="child">
+        /// The child <see cref="Rectangle"/>.
+        /// </param>
+        /// <returns>
+        /// The centered <see cref="Rectangle"/>.
+        /// </returns>
+        public Rectangle CenteredRectangle(Rectangle parent, Rectangle child)
+        {
+            if (parent.Size.Width < child.Size.Width && parent.Size.Height < child.Size.Height)
+            {
+                return parent;
+            }
+
+            int x = (parent.Width - child.Width) / 2;
+            int y = (parent.Height - child.Height) / 2;
+
+            return new Rectangle(x, y, child.Width, child.Height);
+        }
+    }
+}

src/ImageProcessor/Processors/EntropyCrop.cs

@@ -10,7 +10,6 @@ namespace ImageProcessor.Processors
     using System;
     using System.Collections.Generic;
     using System.Drawing;
-    using System.Drawing.Imaging;
 
     using ImageProcessor.Common.Exceptions;
     using ImageProcessor.Imaging;