diff --git a/src/ImageSharp/Formats/WebP/WebPDecoderBase.cs b/src/ImageSharp/Formats/WebP/WebPDecoderBase.cs new file mode 100644 index 000000000..607dbc1c3 --- /dev/null +++ b/src/ImageSharp/Formats/WebP/WebPDecoderBase.cs @@ -0,0 +1,86 @@ +// // Copyright (c) Six Labors and contributors. +// // Licensed under the Apache License, Version 2.0. + +using System; +using System.Buffers; + +using SixLabors.ImageSharp.Memory; + +namespace SixLabors.ImageSharp.Formats.WebP +{ + abstract class WebPDecoderBase + { + protected HTreeGroup[] GetHTreeGroupForPos(Vp8LMetadata metadata, int x, int y) + { + uint metaIndex = this.GetMetaIndex(metadata.HuffmanImage, metadata.HuffmanXSize, metadata.HuffmanSubSampleBits, x, y); + return metadata.HTreeGroups.AsSpan((int)metaIndex).ToArray(); + } + + private uint GetMetaIndex(IMemoryOwner huffmanImage, int xSize, int bits, int x, int y) + { + if (bits is 0) + { + return 0; + } + + Span huffmanImageSpan = huffmanImage.GetSpan(); + return huffmanImageSpan[(xSize * (y >> bits)) + (x >> bits)]; + } + + // TODO: copied from WebPLosslessDecoder + protected int GetCopyDistance(int distanceSymbol, Vp8LBitReader bitReader) + { + if (distanceSymbol < 4) + { + return distanceSymbol + 1; + } + + int extraBits = (distanceSymbol - 2) >> 1; + int offset = (2 + (distanceSymbol & 1)) << extraBits; + + return (int)(offset + bitReader.ReadBits(extraBits) + 1); + } + + // TODO: copied from WebPLosslessDecoder + protected int GetCopyLength(int lengthSymbol, Vp8LBitReader bitReader) + { + // Length and distance prefixes are encoded the same way. + return this.GetCopyDistance(lengthSymbol, bitReader); + } + + // TODO: copied from LosslessDecoder + protected static readonly int[] KCodeToPlane = + { + 0x18, 0x07, 0x17, 0x19, 0x28, 0x06, 0x27, 0x29, 0x16, 0x1a, + 0x26, 0x2a, 0x38, 0x05, 0x37, 0x39, 0x15, 0x1b, 0x36, 0x3a, + 0x25, 0x2b, 0x48, 0x04, 0x47, 0x49, 0x14, 0x1c, 0x35, 0x3b, + 0x46, 0x4a, 0x24, 0x2c, 0x58, 0x45, 0x4b, 0x34, 0x3c, 0x03, + 0x57, 0x59, 0x13, 0x1d, 0x56, 0x5a, 0x23, 0x2d, 0x44, 0x4c, + 0x55, 0x5b, 0x33, 0x3d, 0x68, 0x02, 0x67, 0x69, 0x12, 0x1e, + 0x66, 0x6a, 0x22, 0x2e, 0x54, 0x5c, 0x43, 0x4d, 0x65, 0x6b, + 0x32, 0x3e, 0x78, 0x01, 0x77, 0x79, 0x53, 0x5d, 0x11, 0x1f, + 0x64, 0x6c, 0x42, 0x4e, 0x76, 0x7a, 0x21, 0x2f, 0x75, 0x7b, + 0x31, 0x3f, 0x63, 0x6d, 0x52, 0x5e, 0x00, 0x74, 0x7c, 0x41, + 0x4f, 0x10, 0x20, 0x62, 0x6e, 0x30, 0x73, 0x7d, 0x51, 0x5f, + 0x40, 0x72, 0x7e, 0x61, 0x6f, 0x50, 0x71, 0x7f, 0x60, 0x70 + }; + + protected static readonly int CodeToPlaneCodes = KCodeToPlane.Length; + + protected int PlaneCodeToDistance(int xSize, int planeCode) + { + if (planeCode > CodeToPlaneCodes) + { + return planeCode - CodeToPlaneCodes; + } + + int distCode = KCodeToPlane[planeCode - 1]; + int yOffset = distCode >> 4; + int xOffset = 8 - (distCode & 0xf); + int dist = (yOffset * xSize) + xOffset; + + // dist < 1 can happen if xSize is very small. + return (dist >= 1) ? dist : 1; + } + } +} diff --git a/src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs b/src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs index 3b0a06e5b..851ac213b 100644 --- a/src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs +++ b/src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs @@ -19,7 +19,7 @@ namespace SixLabors.ImageSharp.Formats.WebP /// The lossless specification can be found here: /// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification /// - internal sealed class WebPLosslessDecoder + internal sealed class WebPLosslessDecoder : WebPDecoderBase { private readonly Vp8LBitReader bitReader; @@ -50,24 +50,6 @@ namespace SixLabors.ImageSharp.Formats.WebP private static readonly byte[] KCodeLengthCodeOrder = { 17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }; private static readonly int NumCodeLengthCodes = KCodeLengthCodeOrder.Length; - private static readonly int[] KCodeToPlane = - { - 0x18, 0x07, 0x17, 0x19, 0x28, 0x06, 0x27, 0x29, 0x16, 0x1a, - 0x26, 0x2a, 0x38, 0x05, 0x37, 0x39, 0x15, 0x1b, 0x36, 0x3a, - 0x25, 0x2b, 0x48, 0x04, 0x47, 0x49, 0x14, 0x1c, 0x35, 0x3b, - 0x46, 0x4a, 0x24, 0x2c, 0x58, 0x45, 0x4b, 0x34, 0x3c, 0x03, - 0x57, 0x59, 0x13, 0x1d, 0x56, 0x5a, 0x23, 0x2d, 0x44, 0x4c, - 0x55, 0x5b, 0x33, 0x3d, 0x68, 0x02, 0x67, 0x69, 0x12, 0x1e, - 0x66, 0x6a, 0x22, 0x2e, 0x54, 0x5c, 0x43, 0x4d, 0x65, 0x6b, - 0x32, 0x3e, 0x78, 0x01, 0x77, 0x79, 0x53, 0x5d, 0x11, 0x1f, - 0x64, 0x6c, 0x42, 0x4e, 0x76, 0x7a, 0x21, 0x2f, 0x75, 0x7b, - 0x31, 0x3f, 0x63, 0x6d, 0x52, 0x5e, 0x00, 0x74, 0x7c, 0x41, - 0x4f, 0x10, 0x20, 0x62, 0x6e, 0x30, 0x73, 0x7d, 0x51, 0x5f, - 0x40, 0x72, 0x7e, 0x61, 0x6f, 0x50, 0x71, 0x7f, 0x60, 0x70 - }; - - private static readonly int CodeToPlaneCodes = KCodeToPlane.Length; - private static readonly byte[] KLiteralMap = { 0, 1, 1, 1, 0 @@ -289,10 +271,10 @@ namespace SixLabors.ImageSharp.Formats.WebP { // Backward reference is used. int lengthSym = code - WebPConstants.NumLiteralCodes; - int length = this.GetCopyLength(lengthSym); + int length = this.GetCopyLength(lengthSym, this.bitReader); uint distSymbol = this.ReadSymbol(hTreeGroup[0].HTrees[HuffIndex.Dist]); this.bitReader.FillBitWindow(); - int distCode = this.GetCopyDistance((int)distSymbol); + int distCode = this.GetCopyDistance((int)distSymbol, this.bitReader); int dist = this.PlaneCodeToDistance(width, distCode); if (this.bitReader.IsEndOfStream()) { @@ -767,41 +749,6 @@ namespace SixLabors.ImageSharp.Formats.WebP } } - private int GetCopyDistance(int distanceSymbol) - { - if (distanceSymbol < 4) - { - return distanceSymbol + 1; - } - - int extraBits = (distanceSymbol - 2) >> 1; - int offset = (2 + (distanceSymbol & 1)) << extraBits; - - return (int)(offset + this.bitReader.ReadBits(extraBits) + 1); - } - - private int GetCopyLength(int lengthSymbol) - { - // Length and distance prefixes are encoded the same way. - return this.GetCopyDistance(lengthSymbol); - } - - private int PlaneCodeToDistance(int xSize, int planeCode) - { - if (planeCode > CodeToPlaneCodes) - { - return planeCode - CodeToPlaneCodes; - } - - int distCode = KCodeToPlane[planeCode - 1]; - int yOffset = distCode >> 4; - int xOffset = 8 - (distCode & 0xf); - int dist = (yOffset * xSize) + xOffset; - - // dist < 1 can happen if xSize is very small. - return (dist >= 1) ? dist : 1; - } - private void BuildPackedTable(HTreeGroup hTreeGroup) { for (uint code = 0; code < HuffmanUtils.HuffmanPackedTableSize; ++code) @@ -832,22 +779,5 @@ namespace SixLabors.ImageSharp.Formats.WebP huff.Value |= hCode.Value << shift; return hCode.BitsUsed; } - - private uint GetMetaIndex(IMemoryOwner huffmanImage, int xSize, int bits, int x, int y) - { - if (bits is 0) - { - return 0; - } - - Span huffmanImageSpan = huffmanImage.GetSpan(); - return huffmanImageSpan[(xSize * (y >> bits)) + (x >> bits)]; - } - - private HTreeGroup[] GetHTreeGroupForPos(Vp8LMetadata metadata, int x, int y) - { - uint metaIndex = this.GetMetaIndex(metadata.HuffmanImage, metadata.HuffmanXSize, metadata.HuffmanSubSampleBits, x, y); - return metadata.HTreeGroups.AsSpan((int)metaIndex).ToArray(); - } } } diff --git a/src/ImageSharp/Formats/WebP/WebPLossyDecoder.cs b/src/ImageSharp/Formats/WebP/WebPLossyDecoder.cs index 484f5071f..c1293ff49 100644 --- a/src/ImageSharp/Formats/WebP/WebPLossyDecoder.cs +++ b/src/ImageSharp/Formats/WebP/WebPLossyDecoder.cs @@ -10,7 +10,7 @@ using SixLabors.Memory; namespace SixLabors.ImageSharp.Formats.WebP { - internal sealed class WebPLossyDecoder + internal sealed class WebPLossyDecoder : WebPDecoderBase { private readonly Configuration configuration;