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@ -2,6 +2,7 @@ |
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// Licensed under the Apache License, Version 2.0.
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using System; |
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using System.Buffers; |
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using SixLabors.ImageSharp.Memory; |
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using SixLabors.ImageSharp.PixelFormats; |
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@ -10,13 +11,31 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation |
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internal class YCbCrTiffColor<TPixel> : TiffBaseColorDecoder<TPixel> |
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where TPixel : unmanaged, IPixel<TPixel> |
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{ |
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private readonly MemoryAllocator memoryAllocator; |
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private readonly YCbCrConverter converter; |
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public YCbCrTiffColor(Rational[] referenceBlackAndWhite, Rational[] coefficients) => this.converter = new YCbCrConverter(referenceBlackAndWhite, coefficients); |
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private readonly ushort[] ycbcrSubSampling; |
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public YCbCrTiffColor(MemoryAllocator memoryAllocator, Rational[] referenceBlackAndWhite, Rational[] coefficients, ushort[] ycbcrSubSampling) |
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{ |
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this.memoryAllocator = memoryAllocator; |
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this.converter = new YCbCrConverter(referenceBlackAndWhite, coefficients); |
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this.ycbcrSubSampling = ycbcrSubSampling; |
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} |
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/// <inheritdoc/>
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public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height) |
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{ |
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ReadOnlySpan<byte> ycbcrData = data; |
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if (this.ycbcrSubSampling != null && !(this.ycbcrSubSampling[0] == 1 && this.ycbcrSubSampling[1] == 1)) |
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{ |
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using IMemoryOwner<byte> tmpBuffer = this.memoryAllocator.Allocate<byte>(data.Length); |
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Span<byte> tmpBufferSpan = tmpBuffer.GetSpan(); |
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ReverseChromaSubSampling(width, height, this.ycbcrSubSampling[0], this.ycbcrSubSampling[1], data, tmpBufferSpan); |
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ycbcrData = tmpBufferSpan; |
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} |
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var color = default(TPixel); |
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int offset = 0; |
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for (int y = top; y < top + height; y++) |
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@ -24,12 +43,42 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation |
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Span<TPixel> pixelRow = pixels.GetRowSpan(y).Slice(left, width); |
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for (int x = 0; x < pixelRow.Length; x++) |
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{ |
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Rgba32 rgba = this.converter.ConvertToRgba32(data[offset], data[offset + 1], data[offset + 2]); |
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Rgba32 rgba = this.converter.ConvertToRgba32(ycbcrData[offset], ycbcrData[offset + 1], ycbcrData[offset + 2]); |
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color.FromRgba32(rgba); |
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pixelRow[x] = color; |
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offset += 3; |
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} |
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} |
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} |
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private static void ReverseChromaSubSampling(int width, int height, int horizontalSubSampling, int verticalSubSampling, ReadOnlySpan<byte> source, Span<byte> destination) |
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{ |
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int blockWidth = width / horizontalSubSampling; |
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int blockHeight = height / verticalSubSampling; |
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int cbCrOffsetInBlock = horizontalSubSampling * verticalSubSampling; |
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int blockByteCount = cbCrOffsetInBlock + 2; |
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for (int blockRow = blockHeight - 1; blockRow >= 0; blockRow--) |
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{ |
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for (int blockCol = blockWidth - 1; blockCol >= 0; blockCol--) |
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{ |
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int blockOffset = (blockRow * blockWidth) + blockCol; |
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ReadOnlySpan<byte> blockData = source.Slice(blockOffset * blockByteCount, blockByteCount); |
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byte cr = blockData[cbCrOffsetInBlock + 1]; |
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byte cb = blockData[cbCrOffsetInBlock]; |
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for (int row = verticalSubSampling - 1; row >= 0; row--) |
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{ |
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for (int col = horizontalSubSampling - 1; col >= 0; col--) |
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{ |
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int offset = 3 * ((((blockRow * verticalSubSampling) + row) * width) + (blockCol * horizontalSubSampling) + col); |
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destination[offset + 2] = cr; |
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destination[offset + 1] = cb; |
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destination[offset] = blockData[(row * horizontalSubSampling) + col]; |
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} |
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} |
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} |
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} |
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} |
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} |
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} |
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Brian Popow
5 years ago