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@ -27,6 +27,11 @@ namespace SixLabors.ImageSharp.Processing.Quantization.FrameQuantizers |
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/// </summary>
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private readonly bool singlePass; |
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/// <summary>
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/// The vector representation of the image palette.
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/// </summary>
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private Vector4[] paletteVector; |
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/// <summary>
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/// Initializes a new instance of the <see cref="FrameQuantizerBase{TPixel}"/> class.
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/// </summary>
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@ -35,10 +40,9 @@ namespace SixLabors.ImageSharp.Processing.Quantization.FrameQuantizers |
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/// If true, the quantization process only needs to loop through the source pixels once
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/// </param>
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/// <remarks>
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/// If you construct this class with a true value for singlePass, then the code will, when quantizing your image,
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/// only call the <see cref="FirstPass(ImageFrame{TPixel}, int, int)"/> methods.
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/// If two passes are required, the code will also call <see cref="SecondPass(ImageFrame{TPixel}, Span{byte}, int, int)"/>
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/// and then 'QuantizeImage'.
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/// If you construct this class with a <value>true</value> for <paramref name="singlePass"/>, then the code will
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/// only call the <see cref="SecondPass(ImageFrame{TPixel}, Span{byte}, ReadOnlySpan{TPixel}, int, int)"/> method.
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/// If two passes are required, the code will also call <see cref="FirstPass(ImageFrame{TPixel}, int, int)"/>.
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/// </remarks>
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protected FrameQuantizerBase(IQuantizer quantizer, bool singlePass) |
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{ |
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@ -73,28 +77,31 @@ namespace SixLabors.ImageSharp.Processing.Quantization.FrameQuantizers |
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} |
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// Collect the palette. Required before the second pass runs.
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var quantizedFrame = new QuantizedFrame<TPixel>(image.MemoryAllocator, width, height, this.GetPalette()); |
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TPixel[] palette = this.GetPalette(); |
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this.paletteVector = new Vector4[palette.Length]; |
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PixelOperations<TPixel>.Instance.ToScaledVector4(palette, this.paletteVector, palette.Length); |
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var quantizedFrame = new QuantizedFrame<TPixel>(image.MemoryAllocator, width, height, palette); |
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if (this.Dither) |
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{ |
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// We clone the image as we don't want to alter the original.
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// We clone the image as we don't want to alter the original via dithering.
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using (ImageFrame<TPixel> clone = image.Clone()) |
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{ |
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this.SecondPass(clone, quantizedFrame.GetPixelSpan(), width, height); |
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this.SecondPass(clone, quantizedFrame.GetPixelSpan(), palette, width, height); |
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} |
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} |
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else |
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{ |
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this.SecondPass(image, quantizedFrame.GetPixelSpan(), width, height); |
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this.SecondPass(image, quantizedFrame.GetPixelSpan(), palette, width, height); |
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} |
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return quantizedFrame; |
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} |
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/// <summary>
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/// Execute the first pass through the pixels in the image
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/// Execute the first pass through the pixels in the image to create the palette.
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/// </summary>
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/// <param name="source">The source data</param>
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/// <param name="source">The source data.</param>
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/// <param name="width">The width in pixels of the image.</param>
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/// <param name="height">The height in pixels of the image.</param>
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protected virtual void FirstPass(ImageFrame<TPixel> source, int width, int height) |
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@ -102,17 +109,22 @@ namespace SixLabors.ImageSharp.Processing.Quantization.FrameQuantizers |
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} |
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/// <summary>
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/// Execute a second pass through the image
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/// Execute a second pass through the image to assign the pixels to a palette entry.
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/// </summary>
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/// <param name="source">The source image.</param>
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/// <param name="output">The output pixel array</param>
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/// <param name="width">The width in pixels of the image</param>
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/// <param name="height">The height in pixels of the image</param>
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protected abstract void SecondPass(ImageFrame<TPixel> source, Span<byte> output, int width, int height); |
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/// <param name="output">The output pixel array.</param>
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/// <param name="palette">The output color palette.</param>
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/// <param name="width">The width in pixels of the image.</param>
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/// <param name="height">The height in pixels of the image.</param>
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protected abstract void SecondPass( |
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ImageFrame<TPixel> source, |
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Span<byte> output, |
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ReadOnlySpan<TPixel> palette, |
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int width, |
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int height); |
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/// <summary>
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/// Retrieve the palette for the quantized image.
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/// <remarks>Can be called more than once so make sure calls are cached.</remarks>
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/// </summary>
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/// <returns>
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/// <see cref="T:TPixel[]"/>
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@ -120,13 +132,34 @@ namespace SixLabors.ImageSharp.Processing.Quantization.FrameQuantizers |
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protected abstract TPixel[] GetPalette(); |
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/// <summary>
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/// Returns the closest color from the palette to the given color by calculating the Euclidean distance.
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/// Returns the index of the first instance of the transparent color in the palette.
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/// </summary>
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/// <returns>The <see cref="int"/>.</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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protected byte GetTransparentIndex() |
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{ |
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// Transparent pixels are much more likely to be found at the end of a palette.
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int index = this.paletteVector.Length - 1; |
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for (int i = this.paletteVector.Length - 1; i >= 0; i--) |
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{ |
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ref Vector4 candidate = ref this.paletteVector[i]; |
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if (candidate.Equals(default)) |
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{ |
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index = i; |
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} |
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} |
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return (byte)index; |
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} |
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/// <summary>
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/// Returns the closest color from the palette to the given color by calculating the
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/// Euclidean distance in the Rgba colorspace.
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/// </summary>
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/// <param name="pixel">The color.</param>
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/// <param name="colorPalette">The color palette.</param>
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/// <returns>The <see cref="int"/></returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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protected byte GetClosestPixel(TPixel pixel, TPixel[] colorPalette) |
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protected byte GetClosestPixel(ref TPixel pixel) |
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{ |
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// Check if the color is in the lookup table
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if (this.distanceCache.TryGetValue(pixel, out byte value)) |
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@ -134,22 +167,22 @@ namespace SixLabors.ImageSharp.Processing.Quantization.FrameQuantizers |
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return value; |
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} |
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return this.GetClosestPixelSlow(pixel, colorPalette); |
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return this.GetClosestPixelSlow(ref pixel); |
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} |
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[MethodImpl(MethodImplOptions.NoInlining)] |
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private byte GetClosestPixelSlow(TPixel pixel, TPixel[] colorPalette) |
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private byte GetClosestPixelSlow(ref TPixel pixel) |
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{ |
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// Loop through the palette and find the nearest match.
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int colorIndex = 0; |
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float leastDistance = float.MaxValue; |
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var vector = pixel.ToVector4(); |
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Vector4 vector = pixel.ToScaledVector4(); |
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float epsilon = Constants.EpsilonSquared; |
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for (int index = 0; index < colorPalette.Length; index++) |
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for (int index = 0; index < this.paletteVector.Length; index++) |
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{ |
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ref TPixel candidate = ref colorPalette[index]; |
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float distance = Vector4.DistanceSquared(vector, candidate.ToVector4()); |
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ref Vector4 candidate = ref this.paletteVector[index]; |
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float distance = Vector4.DistanceSquared(vector, candidate); |
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// Greater... Move on.
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if (!(distance < leastDistance)) |
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James Jackson-South
8 years ago