mirror of https://github.com/SixLabors/ImageSharp
Anton Firszov
7 years ago
10 changed files with 370 additions and 242 deletions
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// Copyright (c) Six Labors and contributors.
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// Licensed under the Apache License, Version 2.0.
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using System; |
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using SixLabors.ImageSharp.Advanced; |
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using SixLabors.ImageSharp.PixelFormats; |
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using SixLabors.Primitives; |
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namespace SixLabors.ImageSharp.Processing.Processors.Dithering |
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{ |
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/// <summary>
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/// An <see cref="IImageProcessor{TPixel}"/> that dithers an image using error diffusion.
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/// </summary>
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/// <typeparam name="TPixel">The pixel format.</typeparam>
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internal class ErrorDiffusionPaletteProcessor<TPixel> : PaletteDitherProcessor<TPixel> |
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where TPixel : struct, IPixel<TPixel> |
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{ |
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public ErrorDiffusionPaletteProcessor(ErrorDiffusionPaletteProcessor definition) |
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: base(definition) |
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{ |
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} |
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private new ErrorDiffusionPaletteProcessor Definition => (ErrorDiffusionPaletteProcessor)base.Definition; |
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/// <inheritdoc/>
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protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration) |
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{ |
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byte threshold = (byte)MathF.Round(this.Definition.Threshold * 255F); |
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bool isAlphaOnly = typeof(TPixel) == typeof(Alpha8); |
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var interest = Rectangle.Intersect(sourceRectangle, source.Bounds()); |
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int startY = interest.Y; |
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int endY = interest.Bottom; |
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int startX = interest.X; |
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int endX = interest.Right; |
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// Collect the values before looping so we can reduce our calculation count for identical sibling pixels
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TPixel sourcePixel = source[startX, startY]; |
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TPixel previousPixel = sourcePixel; |
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PixelPair<TPixel> pair = this.GetClosestPixelPair(ref sourcePixel); |
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Rgba32 rgba = default; |
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sourcePixel.ToRgba32(ref rgba); |
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// Convert to grayscale using ITU-R Recommendation BT.709 if required
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byte luminance = isAlphaOnly ? rgba.A : ImageMaths.Get8BitBT709Luminance(rgba.R, rgba.G, rgba.B); |
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for (int y = startY; y < endY; y++) |
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{ |
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Span<TPixel> row = source.GetPixelRowSpan(y); |
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for (int x = startX; x < endX; x++) |
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{ |
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sourcePixel = row[x]; |
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// Check if this is the same as the last pixel. If so use that value
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// rather than calculating it again. This is an inexpensive optimization.
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if (!previousPixel.Equals(sourcePixel)) |
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{ |
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pair = this.GetClosestPixelPair(ref sourcePixel); |
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// No error to spread, exact match.
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if (sourcePixel.Equals(pair.First)) |
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{ |
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continue; |
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} |
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sourcePixel.ToRgba32(ref rgba); |
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luminance = isAlphaOnly ? rgba.A : ImageMaths.Get8BitBT709Luminance(rgba.R, rgba.G, rgba.B); |
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// Setup the previous pointer
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previousPixel = sourcePixel; |
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} |
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TPixel transformedPixel = luminance >= threshold ? pair.Second : pair.First; |
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this.Definition.Diffuser.Dither(source, sourcePixel, transformedPixel, x, y, startX, startY, endX, endY); |
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} |
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} |
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} |
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} |
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} |
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// Copyright (c) Six Labors and contributors.
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// Licensed under the Apache License, Version 2.0.
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using System; |
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using SixLabors.ImageSharp.Advanced; |
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using SixLabors.ImageSharp.PixelFormats; |
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using SixLabors.Primitives; |
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namespace SixLabors.ImageSharp.Processing.Processors.Dithering |
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{ |
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/// <summary>
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/// An <see cref="IImageProcessor{TPixel}"/> that dithers an image using error diffusion.
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/// </summary>
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/// <typeparam name="TPixel">The pixel format.</typeparam>
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internal class OrderedDitherPaletteProcessor<TPixel> : PaletteDitherProcessor<TPixel> |
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where TPixel : struct, IPixel<TPixel> |
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{ |
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public OrderedDitherPaletteProcessor(OrderedDitherPaletteProcessor definition) |
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: base(definition) |
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{ |
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} |
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private new OrderedDitherPaletteProcessor Definition => (OrderedDitherPaletteProcessor)base.Definition; |
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/// <inheritdoc/>
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protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration) |
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{ |
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bool isAlphaOnly = typeof(TPixel) == typeof(Alpha8); |
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var interest = Rectangle.Intersect(sourceRectangle, source.Bounds()); |
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int startY = interest.Y; |
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int endY = interest.Bottom; |
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int startX = interest.X; |
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int endX = interest.Right; |
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// Collect the values before looping so we can reduce our calculation count for identical sibling pixels
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TPixel sourcePixel = source[startX, startY]; |
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TPixel previousPixel = sourcePixel; |
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PixelPair<TPixel> pair = this.GetClosestPixelPair(ref sourcePixel); |
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Rgba32 rgba = default; |
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sourcePixel.ToRgba32(ref rgba); |
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// Convert to grayscale using ITU-R Recommendation BT.709 if required
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byte luminance = isAlphaOnly ? rgba.A : ImageMaths.Get8BitBT709Luminance(rgba.R, rgba.G, rgba.B); |
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for (int y = startY; y < endY; y++) |
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{ |
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Span<TPixel> row = source.GetPixelRowSpan(y); |
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for (int x = startX; x < endX; x++) |
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{ |
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sourcePixel = row[x]; |
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// Check if this is the same as the last pixel. If so use that value
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// rather than calculating it again. This is an inexpensive optimization.
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if (!previousPixel.Equals(sourcePixel)) |
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{ |
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pair = this.GetClosestPixelPair(ref sourcePixel); |
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// No error to spread, exact match.
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if (sourcePixel.Equals(pair.First)) |
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{ |
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continue; |
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} |
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sourcePixel.ToRgba32(ref rgba); |
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luminance = isAlphaOnly ? rgba.A : ImageMaths.Get8BitBT709Luminance(rgba.R, rgba.G, rgba.B); |
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// Setup the previous pointer
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previousPixel = sourcePixel; |
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} |
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this.Definition.Dither.Dither(source, sourcePixel, pair.Second, pair.First, luminance, x, y); |
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} |
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} |
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} |
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} |
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} |
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@ -0,0 +1,37 @@ |
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// Copyright (c) Six Labors and contributors.
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// Licensed under the Apache License, Version 2.0.
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using System; |
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using SixLabors.ImageSharp.PixelFormats; |
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namespace SixLabors.ImageSharp.Processing.Processors.Dithering |
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{ |
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/// <summary>
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/// The base class for dither and diffusion processors that consume a palette.
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/// </summary>
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public abstract class PaletteDitherProcessor : IImageProcessor |
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{ |
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private readonly Color[] palette; |
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/// <summary>
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/// Initializes a new instance of the <see cref="PaletteDitherProcessor"/> class.
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/// </summary>
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/// <param name="palette">The palette to select substitute colors from.</param>
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protected PaletteDitherProcessor(ReadOnlySpan<Color> palette) |
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{ |
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// This shouldn't be a perf issue:
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// these arrays are small, and created with low frequency.
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this.palette = palette.ToArray(); |
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} |
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/// <summary>
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/// Gets the palette to select substitute colors from.
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/// </summary>
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public ReadOnlySpan<Color> Palette => this.palette; |
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/// <inheritdoc />
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public abstract IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>() |
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where TPixel : struct, IPixel<TPixel>; |
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} |
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} |
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