Adding missing halftone method

Former-commit-id: f64a75cf15909739e4eb37638a58b03a2a7cf78a
Former-commit-id: 93dfcfd532f011d666fa8cd551bf15ede1689109

src/ImageProcessor.Web/Configuration/Resources/processing.config.transform

@@ -27,6 +27,7 @@
         <setting key="MaxThreshold" value="100"/>
       </settings>
     </plugin>
+    <plugin name="Halftone" type="ImageProcessor.Web.Processors.Halftone, ImageProcessor.Web"/>
     <plugin name="Hue" type="ImageProcessor.Web.Processors.Hue, ImageProcessor.Web"/>
     <plugin name="Mask" type="ImageProcessor.Web.Processors.Mask, ImageProcessor.Web">
       <settings>

src/ImageProcessor.Web/ImageProcessor.Web.csproj

@@ -55,6 +55,7 @@
     <Compile Include="Helpers\ProcessQueryStringEventArgs.cs" />
     <Compile Include="Processors\DetectEdges.cs" />
     <Compile Include="Processors\EntropyCrop.cs" />
+    <Compile Include="Processors\Halftone.cs" />
     <Compile Include="Processors\Hue.cs" />
     <Compile Include="Processors\Mask.cs" />
     <Compile Include="Processors\Overlay.cs" />

src/ImageProcessor.Web/Processors/Halftone.cs

@@ -0,0 +1,89 @@
+// --------------------------------------------------------------------------------------------------------------------
+// <copyright file="Halftone.cs" company="James South">
+//   Copyright (c) James South.
+//   Licensed under the Apache License, Version 2.0.
+// </copyright>
+// <summary>
+//   The halftone processor applies a classical CMYK halftone to the given image.
+// </summary>
+// --------------------------------------------------------------------------------------------------------------------
+
+namespace ImageProcessor.Web.Processors
+{
+    using System.Text.RegularExpressions;
+
+    using ImageProcessor.Processors;
+
+    /// <summary>
+    /// The halftone processor applies a classical CMYK halftone to the given image.
+    /// </summary>
+    public class Halftone : IWebGraphicsProcessor
+    {
+        /// <summary>
+        /// The regular expression to search strings for.
+        /// </summary>
+        private static readonly Regex QueryRegex = new Regex(@"halftone(=comic)?", RegexOptions.Compiled);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Halftone"/> class.
+        /// </summary>
+        public Halftone()
+        {
+            this.Processor = new ImageProcessor.Processors.Halftone();
+        }
+
+        /// <summary>
+        /// Gets the regular expression to search strings for.
+        /// </summary>
+        public Regex RegexPattern
+        {
+            get
+            {
+                return QueryRegex;
+            }
+        }
+
+        /// <summary>
+        /// Gets the order in which this processor is to be used in a chain.
+        /// </summary>
+        public int SortOrder { get; private set; }
+
+        /// <summary>
+        /// Gets the associated graphics processor.
+        /// </summary>
+        public IGraphicsProcessor Processor { get; private set; }
+
+        /// <summary>
+        /// The position in the original string where the first character of the captured substring was found.
+        /// </summary>
+        /// <param name="queryString">The query string to search.</param>
+        /// <returns>
+        /// The zero-based starting position in the original string where the captured substring was found.
+        /// </returns>
+        public int MatchRegexIndex(string queryString)
+        {
+            int index = 0;
+
+            // Set the sort order to max to allow filtering.
+            this.SortOrder = int.MaxValue;
+
+            foreach (Match match in this.RegexPattern.Matches(queryString))
+            {
+                if (match.Success)
+                {
+                    if (index == 0)
+                    {
+                        // Set the index on the first instance only.
+                        this.SortOrder = match.Index;
+                        bool comicMode = match.Value.Contains("comic");
+                        this.Processor.DynamicParameter = comicMode;
+                    }
+
+                    index += 1;
+                }
+            }
+
+            return this.SortOrder;
+        }
+    }
+}

src/ImageProcessor/Imaging/Colors/CmykColor.cs

@@ -251,13 +251,13 @@ namespace ImageProcessor.Imaging.Colors
 
         /// <summary>
         /// Allows the implicit conversion of an instance of <see cref="CmykColor"/> to a 
-        /// <see cref="System.Drawing.Color"/>.
+        /// <see cref="RgbaColor"/>.
         /// </summary>
         /// <param name="cmykColor">
         /// The instance of <see cref="CmykColor"/> to convert.
         /// </param>
         /// <returns>
-        /// An instance of <see cref="System.Drawing.Color"/>.
+        /// An instance of <see cref="RgbaColor"/>.
         /// </returns>
         public static implicit operator RgbaColor(CmykColor cmykColor)
         {

src/TestWebsites/MVC/config/imageprocessor/processing.config

@@ -27,6 +27,7 @@
         <setting key="MaxThreshold" value="100"/>
       </settings>
     </plugin>
+    <plugin name="Halftone" type="ImageProcessor.Web.Processors.Halftone, ImageProcessor.Web"/>
     <plugin name="Hue" type="ImageProcessor.Web.Processors.Hue, ImageProcessor.Web"/>
     <plugin name="Mask" type="ImageProcessor.Web.Processors.Mask, ImageProcessor.Web">
       <settings>