BackgroundColor

Former-commit-id: abafddef9276f279c204a312c097cd28aa1d3e58
Former-commit-id: 27079155a41cd95690c7b676601e9df4044a05ca
Former-commit-id: 0c77f74fd0194f4bab444d9bb4522422f65ad029

src/ImageProcessorCore/Filters/BackgroundColor.cs

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+// <copyright file="BackgroundColor.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;
+
+    /// <summary>
+    /// Extension methods for the <see cref="Image{T,TP}"/> type.
+    /// </summary>
+    public static partial class ImageExtensions
+    {
+        /// <summary>
+        /// Replaces the background color of image with the given one.
+        /// </summary>
+        /// <typeparam name="T">The pixel format.</typeparam>
+        /// <typeparam name="TP">The packed format. <example>long, float.</example></typeparam>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="color">The color to set as the background.</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> BackgroundColor<T, TP>(this Image<T, TP> source, T color, ProgressEventHandler progressHandler = null)
+            where T : IPackedVector<TP>
+            where TP : struct
+        {
+            BackgroundColorProcessor<T, TP> processor = new BackgroundColorProcessor<T, TP>(color);
+            processor.OnProgress += progressHandler;
+
+            try
+            {
+                return source.Process(source.Bounds, processor);
+            }
+            finally
+            {
+                processor.OnProgress -= progressHandler;
+            }
+        }
+    }
+}

src/ImageProcessorCore/Filters/Processors/BackgroundColorProcessor.cs

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+// <copyright file="BackgroundColorProcessor.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;
+    using System.Numerics;
+    using System.Threading.Tasks;
+
+    /// <summary>
+    /// Sets the background color of the image.
+    /// </summary>
+    public class BackgroundColorProcessor<T, TP> : ImageProcessor<T, TP>
+        where T : IPackedVector<TP>
+        where TP : struct
+    {
+        /// <summary>
+        /// The epsilon for comparing floating point numbers.
+        /// </summary>
+        private const float Epsilon = 0.001f;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="BackgroundColorProcessor{T,TP}"/> class.
+        /// </summary>
+        /// <param name="color">The <see cref="T"/> to set the background color to.</param>
+        public BackgroundColorProcessor(T color)
+        {
+            this.Value = color;
+        }
+
+        /// <summary>
+        /// Gets the background color value.
+        /// </summary>
+        public T 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;
+            Vector4 backgroundColor = this.Value.ToVector4();
+
+            using (IPixelAccessor<T, TP> sourcePixels = source.Lock())
+            using (IPixelAccessor<T, TP> targetPixels = target.Lock())
+            {
+                Parallel.For(
+                    startY,
+                    endY,
+                    Bootstrapper.Instance.ParallelOptions,
+                    y =>
+                        {
+                            if (y >= sourceY && y < sourceBottom)
+                            {
+                                for (int x = startX; x < endX; x++)
+                                {
+                                    Vector4 color = sourcePixels[x, y].ToVector4();
+                                    float a = color.W;
+
+                                    if (a < 1 && a > 0)
+                                    {
+                                        color = Vector4.Lerp(color, backgroundColor, .5f);
+                                    }
+
+                                    if (Math.Abs(a) < Epsilon)
+                                    {
+                                        color = backgroundColor;
+                                    }
+
+                                    T packed = default(T);
+                                    packed.PackVector(color);
+                                    targetPixels[x, y] = packed;
+                                }
+
+                                this.OnRowProcessed();
+                            }
+                        });
+            }
+        }
+    }
+}

tests/ImageProcessorCore.Tests/Processors/Filters/BackgroundColorTest.cs

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+// <copyright file="BackgroundColorTest.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 BackgroundColorTest : FileTestBase
+    {
+        [Fact]
+        public void ImageShouldApplyBackgroundColorFilter()
+        {
+            const string path = "TestOutput/BackgroundColor";
+            if (!Directory.Exists(path))
+            {
+                Directory.CreateDirectory(path);
+            }
+
+            foreach (string file in Files)
+            {
+                using (FileStream stream = File.OpenRead(file))
+                {
+                    string filename = Path.GetFileName(file);
+                    Image image = new Image(stream);
+                    using (FileStream output = File.OpenWrite($"{path}/{filename}"))
+                    {
+                        image.BackgroundColor(Color.HotPink)
+                             .Save(output);
+                    }
+                }
+            }
+        }
+    }
+}