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63 lines
2.5 KiB
63 lines
2.5 KiB
// Copyright (c) Six Labors.
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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.Quantization
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{
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/// <summary>
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/// Allows the quantization of images pixels using color palettes.
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/// </summary>
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public class PaletteQuantizer : IQuantizer
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{
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private readonly ReadOnlyMemory<Color> colorPalette;
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/// <summary>
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/// Initializes a new instance of the <see cref="PaletteQuantizer"/> class.
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/// </summary>
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/// <param name="palette">The color palette.</param>
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public PaletteQuantizer(ReadOnlyMemory<Color> palette)
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: this(palette, new QuantizerOptions())
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{
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="PaletteQuantizer"/> class.
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/// </summary>
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/// <param name="palette">The color palette.</param>
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/// <param name="options">The quantizer options defining quantization rules.</param>
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public PaletteQuantizer(ReadOnlyMemory<Color> palette, QuantizerOptions options)
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{
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Guard.MustBeGreaterThan(palette.Length, 0, nameof(palette));
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Guard.NotNull(options, nameof(options));
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this.colorPalette = palette;
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this.Options = options;
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}
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/// <inheritdoc />
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public QuantizerOptions Options { get; }
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/// <inheritdoc />
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public IQuantizer<TPixel> CreatePixelSpecificQuantizer<TPixel>(Configuration configuration)
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where TPixel : unmanaged, IPixel<TPixel>
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=> this.CreatePixelSpecificQuantizer<TPixel>(configuration, this.Options);
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/// <inheritdoc />
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public IQuantizer<TPixel> CreatePixelSpecificQuantizer<TPixel>(Configuration configuration, QuantizerOptions options)
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where TPixel : unmanaged, IPixel<TPixel>
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{
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Guard.NotNull(options, nameof(options));
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// The palette quantizer can reuse the same pixel map across multiple frames
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// since the palette is unchanging. This allows a reduction of memory usage across
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// multi frame gifs using a global palette.
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int length = Math.Min(this.colorPalette.Length, options.MaxColors);
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var palette = new TPixel[length];
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Color.ToPixel(configuration, this.colorPalette.Span, palette.AsSpan());
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return new PaletteQuantizer<TPixel>(configuration, options, palette);
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}
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}
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}
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