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@ -17,6 +17,13 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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/// </summary>
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internal static unsafe class PredictorEncoder |
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{ |
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private static readonly sbyte[] DeltaLut = { 16, 16, 8, 4, 2, 2, 2 }; |
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private static readonly sbyte[][] Offset = |
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{ |
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new sbyte[] { 0, -1 }, new sbyte[] { 0, 1 }, new sbyte[] { -1, 0 }, new sbyte[] { 1, 0 }, new sbyte[] { -1, -1 }, new sbyte[] { -1, 1 }, new sbyte[] { 1, -1 }, new sbyte[] { 1, 1 } |
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}; |
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private const int GreenRedToBlueNumAxis = 8; |
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private const int GreenRedToBlueMaxIters = 7; |
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@ -41,6 +48,8 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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Span<uint> bgra, |
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Span<uint> bgraScratch, |
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Span<uint> image, |
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int[][] histoArgb, |
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int[][] bestHisto, |
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bool nearLossless, |
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int nearLosslessQuality, |
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WebpTransparentColorMode transparentColorMode, |
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@ -80,6 +89,8 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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histo, |
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bgraScratch, |
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bgra, |
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histoArgb, |
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bestHisto, |
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maxQuantization, |
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transparentColorMode, |
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usedSubtractGreen, |
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@ -105,7 +116,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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lowEffort); |
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} |
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public static void ColorSpaceTransform(int width, int height, int bits, int quality, Span<uint> bgra, Span<uint> image) |
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public static void ColorSpaceTransform(int width, int height, int bits, int quality, Span<uint> bgra, Span<uint> image, Span<int> scratch) |
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{ |
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int maxTileSize = 1 << bits; |
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int tileXSize = LosslessUtils.SubSampleSize(width, bits); |
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@ -139,7 +150,8 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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height, |
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accumulatedRedHisto, |
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accumulatedBlueHisto, |
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bgra); |
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bgra, |
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scratch); |
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image[offset] = MultipliersToColorCode(prevX); |
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CopyTileWithColorTransform(width, height, tileXOffset, tileYOffset, maxTileSize, prevX, bgra); |
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@ -188,6 +200,8 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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int[][] accumulated, |
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Span<uint> argbScratch, |
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Span<uint> argb, |
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int[][] histoArgb, |
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int[][] bestHisto, |
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int maxQuantization, |
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WebpTransparentColorMode transparentColorMode, |
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bool usedSubtractGreen, |
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@ -222,21 +236,14 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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float bestDiff = MaxDiffCost; |
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int bestMode = 0; |
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uint[] residuals = new uint[1 << WebpConstants.MaxTransformBits]; |
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int[][] histoArgb = new int[4][]; |
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int[][] bestHisto = new int[4][]; |
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for (int i = 0; i < 4; i++) |
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{ |
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histoArgb[i] = new int[256]; |
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bestHisto[i] = new int[256]; |
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histoArgb[i].AsSpan().Clear(); |
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bestHisto[i].AsSpan().Clear(); |
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} |
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for (int mode = 0; mode < numPredModes; mode++) |
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{ |
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for (int i = 0; i < 4; i++) |
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{ |
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histoArgb[i].AsSpan().Fill(0); |
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} |
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if (startY > 0) |
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{ |
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// Read the row above the tile which will become the first upper_row.
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@ -300,6 +307,11 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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bestDiff = curDiff; |
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bestMode = mode; |
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} |
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for (int i = 0; i < 4; i++) |
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{ |
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histoArgb[i].AsSpan().Clear(); |
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} |
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} |
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for (int i = 0; i < 4; i++) |
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@ -819,7 +831,19 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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} |
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} |
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private static Vp8LMultipliers GetBestColorTransformForTile(int tileX, int tileY, int bits, Vp8LMultipliers prevX, Vp8LMultipliers prevY, int quality, int xSize, int ySize, int[] accumulatedRedHisto, int[] accumulatedBlueHisto, Span<uint> argb) |
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private static Vp8LMultipliers GetBestColorTransformForTile( |
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int tileX, |
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int tileY, |
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int bits, |
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Vp8LMultipliers prevX, |
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Vp8LMultipliers prevY, |
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int quality, |
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int xSize, |
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int ySize, |
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int[] accumulatedRedHisto, |
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int[] accumulatedBlueHisto, |
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Span<uint> argb, |
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Span<int> scratch) |
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{ |
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int maxTileSize = 1 << bits; |
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int tileYOffset = tileY * maxTileSize; |
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@ -832,18 +856,28 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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var bestTx = default(Vp8LMultipliers); |
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GetBestGreenToRed(tileArgb, xSize, tileWidth, tileHeight, prevX, prevY, quality, accumulatedRedHisto, ref bestTx); |
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GetBestGreenToRed(tileArgb, xSize, scratch, tileWidth, tileHeight, prevX, prevY, quality, accumulatedRedHisto, ref bestTx); |
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GetBestGreenRedToBlue(tileArgb, xSize, tileWidth, tileHeight, prevX, prevY, quality, accumulatedBlueHisto, ref bestTx); |
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GetBestGreenRedToBlue(tileArgb, xSize, scratch, tileWidth, tileHeight, prevX, prevY, quality, accumulatedBlueHisto, ref bestTx); |
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return bestTx; |
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} |
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private static void GetBestGreenToRed(Span<uint> argb, int stride, int tileWidth, int tileHeight, Vp8LMultipliers prevX, Vp8LMultipliers prevY, int quality, int[] accumulatedRedHisto, ref Vp8LMultipliers bestTx) |
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private static void GetBestGreenToRed( |
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Span<uint> argb, |
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int stride, |
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Span<int> scratch, |
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int tileWidth, |
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int tileHeight, |
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Vp8LMultipliers prevX, |
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Vp8LMultipliers prevY, |
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int quality, |
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int[] accumulatedRedHisto, |
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ref Vp8LMultipliers bestTx) |
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{ |
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int maxIters = 4 + ((7 * quality) >> 8); // in range [4..6]
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int greenToRedBest = 0; |
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double bestDiff = GetPredictionCostCrossColorRed(argb, stride, tileWidth, tileHeight, prevX, prevY, greenToRedBest, accumulatedRedHisto); |
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double bestDiff = GetPredictionCostCrossColorRed(argb, stride, scratch, tileWidth, tileHeight, prevX, prevY, greenToRedBest, accumulatedRedHisto); |
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for (int iter = 0; iter < maxIters; iter++) |
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{ |
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// ColorTransformDelta is a 3.5 bit fixed point, so 32 is equal to
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@ -855,7 +889,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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for (int offset = -delta; offset <= delta; offset += 2 * delta) |
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{ |
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int greenToRedCur = offset + greenToRedBest; |
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double curDiff = GetPredictionCostCrossColorRed(argb, stride, tileWidth, tileHeight, prevX, prevY, greenToRedCur, accumulatedRedHisto); |
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double curDiff = GetPredictionCostCrossColorRed(argb, stride, scratch, tileWidth, tileHeight, prevX, prevY, greenToRedCur, accumulatedRedHisto); |
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if (curDiff < bestDiff) |
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{ |
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bestDiff = curDiff; |
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@ -867,24 +901,22 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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bestTx.GreenToRed = (byte)(greenToRedBest & 0xff); |
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} |
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private static void GetBestGreenRedToBlue(Span<uint> argb, int stride, int tileWidth, int tileHeight, Vp8LMultipliers prevX, Vp8LMultipliers prevY, int quality, int[] accumulatedBlueHisto, ref Vp8LMultipliers bestTx) |
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private static void GetBestGreenRedToBlue(Span<uint> argb, int stride, Span<int> scratch, int tileWidth, int tileHeight, Vp8LMultipliers prevX, Vp8LMultipliers prevY, int quality, int[] accumulatedBlueHisto, ref Vp8LMultipliers bestTx) |
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{ |
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int iters = (quality < 25) ? 1 : (quality > 50) ? GreenRedToBlueMaxIters : 4; |
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int greenToBlueBest = 0; |
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int redToBlueBest = 0; |
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sbyte[][] offset = { new sbyte[] { 0, -1 }, new sbyte[] { 0, 1 }, new sbyte[] { -1, 0 }, new sbyte[] { 1, 0 }, new sbyte[] { -1, -1 }, new sbyte[] { -1, 1 }, new sbyte[] { 1, -1 }, new sbyte[] { 1, 1 } }; |
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sbyte[] deltaLut = { 16, 16, 8, 4, 2, 2, 2 }; |
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// Initial value at origin:
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double bestDiff = GetPredictionCostCrossColorBlue(argb, stride, tileWidth, tileHeight, prevX, prevY, greenToBlueBest, redToBlueBest, accumulatedBlueHisto); |
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double bestDiff = GetPredictionCostCrossColorBlue(argb, stride, scratch, tileWidth, tileHeight, prevX, prevY, greenToBlueBest, redToBlueBest, accumulatedBlueHisto); |
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for (int iter = 0; iter < iters; iter++) |
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{ |
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int delta = deltaLut[iter]; |
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int delta = DeltaLut[iter]; |
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for (int axis = 0; axis < GreenRedToBlueNumAxis; axis++) |
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{ |
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int greenToBlueCur = (offset[axis][0] * delta) + greenToBlueBest; |
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int redToBlueCur = (offset[axis][1] * delta) + redToBlueBest; |
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double curDiff = GetPredictionCostCrossColorBlue(argb, stride, tileWidth, tileHeight, prevX, prevY, greenToBlueCur, redToBlueCur, accumulatedBlueHisto); |
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int greenToBlueCur = (Offset[axis][0] * delta) + greenToBlueBest; |
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int redToBlueCur = (Offset[axis][1] * delta) + redToBlueBest; |
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double curDiff = GetPredictionCostCrossColorBlue(argb, stride, scratch, tileWidth, tileHeight, prevX, prevY, greenToBlueCur, redToBlueCur, accumulatedBlueHisto); |
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if (curDiff < bestDiff) |
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{ |
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bestDiff = curDiff; |
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@ -910,9 +942,19 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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bestTx.RedToBlue = (byte)(redToBlueBest & 0xff); |
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} |
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private static double GetPredictionCostCrossColorRed(Span<uint> argb, int stride, int tileWidth, int tileHeight, Vp8LMultipliers prevX, Vp8LMultipliers prevY, int greenToRed, int[] accumulatedRedHisto) |
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private static double GetPredictionCostCrossColorRed( |
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Span<uint> argb, |
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int stride, |
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Span<int> scratch, |
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int tileWidth, |
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int tileHeight, |
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Vp8LMultipliers prevX, |
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Vp8LMultipliers prevY, |
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int greenToRed, |
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int[] accumulatedRedHisto) |
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{ |
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int[] histo = new int[256]; |
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Span<int> histo = scratch.Slice(0, 256); |
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histo.Clear(); |
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CollectColorRedTransforms(argb, stride, tileWidth, tileHeight, greenToRed, histo); |
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double curDiff = PredictionCostCrossColor(accumulatedRedHisto, histo); |
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@ -937,9 +979,20 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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return curDiff; |
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} |
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private static double GetPredictionCostCrossColorBlue(Span<uint> argb, int stride, int tileWidth, int tileHeight, Vp8LMultipliers prevX, Vp8LMultipliers prevY, int greenToBlue, int redToBlue, int[] accumulatedBlueHisto) |
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private static double GetPredictionCostCrossColorBlue( |
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Span<uint> argb, |
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int stride, |
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Span<int> scratch, |
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int tileWidth, |
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int tileHeight, |
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Vp8LMultipliers prevX, |
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Vp8LMultipliers prevY, |
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int greenToBlue, |
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int redToBlue, |
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int[] accumulatedBlueHisto) |
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{ |
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int[] histo = new int[256]; |
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Span<int> histo = scratch.Slice(0, 256); |
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histo.Clear(); |
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CollectColorBlueTransforms(argb, stride, tileWidth, tileHeight, greenToBlue, redToBlue, histo); |
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double curDiff = PredictionCostCrossColor(accumulatedBlueHisto, histo); |
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@ -980,7 +1033,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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return curDiff; |
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} |
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private static void CollectColorRedTransforms(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToRed, int[] histo) |
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private static void CollectColorRedTransforms(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToRed, Span<int> histo) |
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{ |
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#if SUPPORTS_RUNTIME_INTRINSICS
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if (Sse41.IsSupported) |
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@ -1036,7 +1089,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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} |
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} |
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private static void CollectColorRedTransformsNoneVectorized(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToRed, int[] histo) |
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private static void CollectColorRedTransformsNoneVectorized(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToRed, Span<int> histo) |
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{ |
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int pos = 0; |
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while (tileHeight-- > 0) |
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@ -1051,7 +1104,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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} |
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} |
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private static void CollectColorBlueTransforms(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToBlue, int redToBlue, int[] histo) |
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private static void CollectColorBlueTransforms(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToBlue, int redToBlue, Span<int> histo) |
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{ |
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#if SUPPORTS_RUNTIME_INTRINSICS
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if (Sse41.IsSupported) |
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@ -1114,7 +1167,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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} |
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} |
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private static void CollectColorBlueTransformsNoneVectorized(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToBlue, int redToBlue, int[] histo) |
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private static void CollectColorBlueTransformsNoneVectorized(Span<uint> bgra, int stride, int tileWidth, int tileHeight, int greenToBlue, int redToBlue, Span<int> histo) |
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{ |
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int pos = 0; |
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while (tileHeight-- > 0) |
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@ -1143,7 +1196,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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} |
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[MethodImpl(InliningOptions.ShortMethod)] |
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private static double PredictionCostCrossColor(int[] accumulated, int[] counts) |
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private static double PredictionCostCrossColor(int[] accumulated, Span<int> counts) |
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{ |
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// Favor low entropy, locally and globally.
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// Favor small absolute values for PredictionCostSpatial.
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@ -1152,7 +1205,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless |
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} |
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[MethodImpl(InliningOptions.ShortMethod)] |
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private static float PredictionCostSpatial(int[] counts, int weight0, double expVal) |
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private static float PredictionCostSpatial(Span<int> counts, int weight0, double expVal) |
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{ |
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int significantSymbols = 256 >> 4; |
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double expDecayFactor = 0.6; |
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Brian Popow
5 years ago