From b8cc804a531398fa18c656e201ad47343a92be02 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Sat, 30 Jul 2016 10:35:53 +1000
Subject: [PATCH] Pixelate

Former-commit-id: e1687a44c91ad29a9a20aa0ac0a5f6bf640c7202
Former-commit-id: d536480c39f7f575a40279ab96f7d7312a9dee91
Former-commit-id: 2ca77c98a64414096b01f4e41221ab17bea2ddeb
---
 src/ImageProcessorCore/Filters/Pixelate.cs    | 64 ++++++++++++
 .../Filters/Processors/PixelateProcessor.cs   | 97 +++++++++++++++++++
 .../Processors/Filters/PixelateTest.cs        | 47 +++++++++
 3 files changed, 208 insertions(+)
 create mode 100644 src/ImageProcessorCore/Filters/Pixelate.cs
 create mode 100644 src/ImageProcessorCore/Filters/Processors/PixelateProcessor.cs
 create mode 100644 tests/ImageProcessorCore.Tests/Processors/Filters/PixelateTest.cs

diff --git a/src/ImageProcessorCore/Filters/Pixelate.cs b/src/ImageProcessorCore/Filters/Pixelate.cs
new file mode 100644
index 000000000..8bfb7cd2d
--- /dev/null
+++ b/src/ImageProcessorCore/Filters/Pixelate.cs
@@ -0,0 +1,64 @@
+// <copyright file="Pixelate.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessorCore
+{
+    using Processors;
+    using System;
+
+    /// <summary>
+    /// Extension methods for the <see cref="Image{T,TP}"/> type.
+    /// </summary>
+    /// <typeparam name="T">The pixel format.</typeparam>
+    /// <typeparam name="TP">The packed format. <example>long, float.</example></typeparam>
+    public static partial class ImageExtensions
+    {
+        /// <summary>
+        /// Pixelates and image with the given pixel size.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="size">The size of the pixels.</param>
+        /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
+        /// <returns>The <see cref="Image{T,TP}"/>.</returns>
+        public static Image<T, TP> Pixelate<T, TP>(this Image<T, TP> source, int size = 4, ProgressEventHandler progressHandler = null)
+            where T : IPackedVector<TP>
+            where TP : struct
+        {
+            return Pixelate(source, size, source.Bounds, progressHandler);
+        }
+
+        /// <summary>
+        /// Pixelates and image with the given pixel size.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="size">The size of the pixels.</param>
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
+        /// </param>
+        /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
+        /// <returns>The <see cref="Image{T,TP}"/>.</returns>
+        public static Image<T, TP> Pixelate<T, TP>(this Image<T, TP> source, int size, Rectangle rectangle, ProgressEventHandler progressHandler = null)
+            where T : IPackedVector<TP>
+            where TP : struct
+        {
+            if (size <= 0 || size > source.Height || size > source.Width)
+            {
+                throw new ArgumentOutOfRangeException(nameof(size));
+            }
+
+            PixelateProcessor<T, TP> processor = new PixelateProcessor<T, TP>(size);
+            processor.OnProgress += progressHandler;
+
+            try
+            {
+                return source.Process(rectangle, processor);
+            }
+            finally
+            {
+                processor.OnProgress -= progressHandler;
+            }
+        }
+    }
+}
diff --git a/src/ImageProcessorCore/Filters/Processors/PixelateProcessor.cs b/src/ImageProcessorCore/Filters/Processors/PixelateProcessor.cs
new file mode 100644
index 000000000..816ce2f42
--- /dev/null
+++ b/src/ImageProcessorCore/Filters/Processors/PixelateProcessor.cs
@@ -0,0 +1,97 @@
+// <copyright file="PixelateProcessor.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessorCore.Processors
+{
+    using System.Collections.Generic;
+    using System.Threading.Tasks;
+
+    /// <summary>
+    /// An <see cref="IImageProcessor{T,TP}"/> to invert the colors of an <see cref="Image{T,TP}"/>.
+    /// </summary>
+    /// <typeparam name="T">The pixel format.</typeparam>
+    /// <typeparam name="TP">The packed format. <example>long, float.</example></typeparam>
+    public class PixelateProcessor<T, TP> : ImageProcessor<T, TP>
+        where T : IPackedVector<TP>
+        where TP : struct
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PixelateProcessor{T,TP}"/> class.
+        /// </summary>
+        /// <param name="size">The size of the pixels. Must be greater than 0.</param>
+        /// <exception cref="System.ArgumentException">
+        /// <paramref name="size"/> is less than 0 or equal to 0.
+        /// </exception>
+        public PixelateProcessor(int size)
+        {
+            Guard.MustBeGreaterThan(size, 0, nameof(size));
+            this.Value = size;
+        }
+
+        /// <summary>
+        /// Gets or the pixel size.
+        /// </summary>
+        public int Value { get; }
+
+        /// <inheritdoc/>
+        protected override void Apply(ImageBase<T, TP> target, ImageBase<T, TP> source, Rectangle targetRectangle, Rectangle sourceRectangle, int startY, int endY)
+        {
+            int sourceY = sourceRectangle.Y;
+            int sourceBottom = sourceRectangle.Bottom;
+            int startX = sourceRectangle.X;
+            int endX = sourceRectangle.Right;
+            int size = this.Value;
+            int offset = this.Value / 2;
+
+            // Get the range on the y-plane to choose from.
+            IEnumerable<int> range = EnumerableExtensions.SteppedRange(startY, i => i < endY, size);
+
+            using (IPixelAccessor<T, TP> sourcePixels = source.Lock())
+            using (IPixelAccessor<T, TP> targetPixels = target.Lock())
+            {
+                Parallel.ForEach(
+                    range,
+                    y =>
+                        {
+                            if (y >= sourceY && y < sourceBottom)
+                            {
+                                for (int x = startX; x < endX; x += size)
+                                {
+                                    int offsetX = offset;
+                                    int offsetY = offset;
+
+                                    // Make sure that the offset is within the boundary of the 
+                                    // image.
+                                    while (y + offsetY >= sourceBottom)
+                                    {
+                                        offsetY--;
+                                    }
+
+                                    while (x + offsetX >= endX)
+                                    {
+                                        offsetX--;
+                                    }
+
+                                    // Get the pixel color in the centre of the soon to be pixelated area.
+                                    // ReSharper disable AccessToDisposedClosure
+                                    T pixel = sourcePixels[x + offsetX, y + offsetY];
+
+                                    // For each pixel in the pixelate size, set it to the centre color.
+                                    for (int l = y; l < y + size && l < sourceBottom; l++)
+                                    {
+                                        for (int k = x; k < x + size && k < endX; k++)
+                                        {
+                                            targetPixels[k, l] = pixel;
+                                        }
+                                    }
+                                }
+
+                                this.OnRowProcessed();
+                            }
+                        });
+            }
+        }
+    }
+}
diff --git a/tests/ImageProcessorCore.Tests/Processors/Filters/PixelateTest.cs b/tests/ImageProcessorCore.Tests/Processors/Filters/PixelateTest.cs
new file mode 100644
index 000000000..b2ef2fb38
--- /dev/null
+++ b/tests/ImageProcessorCore.Tests/Processors/Filters/PixelateTest.cs
@@ -0,0 +1,47 @@
+// <copyright file="PixelateTest.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessorCore.Tests
+{
+    using System.IO;
+
+    using Xunit;
+
+    public class PixelateTest : FileTestBase
+    {
+        public static readonly TheoryData<int> PixelateValues
+        = new TheoryData<int>
+        {
+            4 ,
+            8 ,
+        };
+
+        [Theory]
+        [MemberData("PixelateValues")]
+        public void ImageShouldApplyPixelateFilter(int value)
+        {
+            const string path = "TestOutput/Pixelate";
+            if (!Directory.Exists(path))
+            {
+                Directory.CreateDirectory(path);
+            }
+
+            foreach (string file in Files)
+            {
+                using (FileStream stream = File.OpenRead(file))
+                {
+                    string filename = Path.GetFileNameWithoutExtension(file) + "-" + value + Path.GetExtension(file);
+
+                    Image image = new Image(stream);
+                    using (FileStream output = File.OpenWrite($"{path}/{filename}"))
+                    {
+                        image.Pixelate(value)
+                             .Save(output);
+                    }
+                }
+            }
+        }
+    }
+}
\ No newline at end of file