mirror of https://github.com/SixLabors/ImageSharp
Brian Popow
4 years ago
11 changed files with 256 additions and 41 deletions
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// Copyright (c) Six Labors.
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// Licensed under the Six Labors Split License.
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using System.Buffers; |
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using System.Runtime.InteropServices; |
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using SixLabors.ImageSharp.IO; |
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using SixLabors.ImageSharp.Memory; |
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namespace SixLabors.ImageSharp.Formats.OpenExr.Compression.Decompressors; |
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internal class B44Compression : ExrBaseDecompressor |
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{ |
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private readonly int width; |
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private readonly int height; |
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private readonly uint rowsPerBlock; |
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private readonly int channelCount; |
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private byte[] scratch = new byte[14]; |
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private ushort[] s = new ushort[16]; |
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private IMemoryOwner<ushort> tmpBuffer; |
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public B44Compression(MemoryAllocator allocator, uint uncompressedBytes, int width, int height, uint rowsPerBlock, int channelCount) |
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: base(allocator, uncompressedBytes) |
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{ |
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this.width = width; |
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this.height = height; |
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this.rowsPerBlock = rowsPerBlock; |
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this.channelCount = channelCount; |
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this.tmpBuffer = allocator.Allocate<ushort>((int)(width * rowsPerBlock * channelCount)); |
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} |
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public override void Decompress(BufferedReadStream stream, uint compressedBytes, Span<byte> buffer) |
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{ |
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Span<ushort> outputBuffer = MemoryMarshal.Cast<byte, ushort>(buffer); |
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Span<ushort> decompressed = this.tmpBuffer.GetSpan(); |
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int outputOffset = 0; |
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int bytesLeft = (int)compressedBytes; |
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for (int i = 0; i < this.channelCount && bytesLeft > 0; i++) |
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{ |
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for (int y = 0; y < this.rowsPerBlock; y += 4) |
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{ |
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Span<ushort> row0 = decompressed.Slice(outputOffset, this.width); |
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outputOffset += this.width; |
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Span<ushort> row1 = decompressed.Slice(outputOffset, this.width); |
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outputOffset += this.width; |
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Span<ushort> row2 = decompressed.Slice(outputOffset, this.width); |
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outputOffset += this.width; |
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Span<ushort> row3 = decompressed.Slice(outputOffset, this.width); |
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outputOffset += this.width; |
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int rowOffset = 0; |
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for (int x = 0; x < this.width && bytesLeft > 0; x += 4) |
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{ |
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int bytesRead = stream.Read(this.scratch, 0, 3); |
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if (bytesRead == 0) |
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{ |
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ExrThrowHelper.ThrowInvalidImageContentException("Could not read enough data from the stream"); |
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} |
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if (this.scratch[2] >= 13 << 2) |
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{ |
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Unpack3(this.scratch, this.s); |
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bytesLeft -= 3; |
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} |
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else |
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{ |
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bytesRead = stream.Read(this.scratch, 3, 11); |
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if (bytesRead == 0) |
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{ |
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ExrThrowHelper.ThrowInvalidImageContentException("Could not read enough data from the stream"); |
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} |
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Unpack14(this.scratch, this.s); |
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bytesLeft -= 14; |
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} |
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int n = x + 3 < this.width ? 4 : this.width - x; |
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if (y + 3 < this.rowsPerBlock) |
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{ |
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this.s.AsSpan(0, n).CopyTo(row0.Slice(rowOffset)); |
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this.s.AsSpan(4, n).CopyTo(row1.Slice(rowOffset)); |
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this.s.AsSpan(8, n).CopyTo(row2.Slice(rowOffset)); |
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this.s.AsSpan(12, n).CopyTo(row3.Slice(rowOffset)); |
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} |
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else |
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{ |
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this.s.AsSpan(0, n).CopyTo(row0.Slice(rowOffset)); |
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if (y + 1 < this.rowsPerBlock) |
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{ |
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this.s.AsSpan(4, n).CopyTo(row1.Slice(rowOffset)); |
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} |
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if (y + 2 < this.rowsPerBlock) |
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{ |
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this.s.AsSpan(8, n).CopyTo(row2.Slice(rowOffset)); |
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} |
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} |
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rowOffset += 4; |
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} |
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if (bytesLeft <= 0) |
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{ |
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break; |
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} |
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} |
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} |
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// Rearrange the decompressed data such that the data for each scan line form a contiguous block.
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int offsetDecompressed = 0; |
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int offsetOutput = 0; |
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int blockSize = (int)(this.width * this.rowsPerBlock); |
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for (int y = 0; y < this.rowsPerBlock; y++) |
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{ |
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for (int i = 0; i < this.channelCount; i++) |
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{ |
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decompressed.Slice(offsetDecompressed + (i * blockSize), this.width).CopyTo(outputBuffer.Slice(offsetOutput)); |
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offsetOutput += this.width; |
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} |
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offsetDecompressed += this.width; |
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} |
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} |
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// Unpack a 14-byte block into 4 by 4 16-bit pixels.
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private static void Unpack14(Span<byte> b, Span<ushort> s) |
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{ |
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s[0] = (ushort)((b[0] << 8) | b[1]); |
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ushort shift = (ushort)(b[2] >> 2); |
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ushort bias = (ushort)(0x20u << shift); |
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s[4] = (ushort)(s[0] + ((((b[2] << 4) | (b[3] >> 4)) & 0x3fu) << shift) - bias); |
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s[8] = (ushort)(s[4] + ((((b[3] << 2) | (b[4] >> 6)) & 0x3fu) << shift) - bias); |
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s[12] = (ushort)(s[8] + ((b[4] & 0x3fu) << shift) - bias); |
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s[1] = (ushort)(s[0] + ((uint)(b[5] >> 2) << shift) - bias); |
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s[5] = (ushort)(s[4] + ((((b[5] << 4) | (b[6] >> 4)) & 0x3fu) << shift) - bias); |
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s[9] = (ushort)(s[8] + ((((b[6] << 2) | (b[7] >> 6)) & 0x3fu) << shift) - bias); |
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s[13] = (ushort)(s[12] + ((b[7] & 0x3fu) << shift) - bias); |
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s[2] = (ushort)(s[1] + ((uint)(b[8] >> 2) << shift) - bias); |
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s[6] = (ushort)(s[5] + ((((b[8] << 4) | (b[9] >> 4)) & 0x3fu) << shift) - bias); |
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s[10] = (ushort)(s[9] + ((((b[9] << 2) | (b[10] >> 6)) & 0x3fu) << shift) - bias); |
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s[14] = (ushort)(s[13] + ((b[10] & 0x3fu) << shift) - bias); |
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s[3] = (ushort)(s[2] + ((uint)(b[11] >> 2) << shift) - bias); |
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s[7] = (ushort)(s[6] + ((((b[11] << 4) | (b[12] >> 4)) & 0x3fu) << shift) - bias); |
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s[11] = (ushort)(s[10] + ((((b[12] << 2) | (b[13] >> 6)) & 0x3fu) << shift) - bias); |
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s[15] = (ushort)(s[14] + ((b[13] & 0x3fu) << shift) - bias); |
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for (int i = 0; i < 16; ++i) |
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{ |
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if ((s[i] & 0x8000) != 0) |
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{ |
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s[i] &= 0x7fff; |
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} |
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else |
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{ |
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s[i] = (ushort)~s[i]; |
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} |
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} |
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} |
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// Unpack a 3-byte block into 4 by 4 identical 16-bit pixels.
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private static void Unpack3(Span<byte> b, Span<ushort> s) |
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{ |
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s[0] = (ushort)((b[0] << 8) | b[1]); |
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if ((s[0] & 0x8000) != 0) |
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{ |
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s[0] &= 0x7fff; |
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} |
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else |
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{ |
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s[0] = (ushort)~s[0]; |
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} |
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for (int i = 1; i < 16; ++i) |
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{ |
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s[i] = s[0]; |
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} |
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} |
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protected override void Dispose(bool disposing) => this.tmpBuffer.Dispose(); |
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} |
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@ -0,0 +1,3 @@ |
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version https://git-lfs.github.com/spec/v1 |
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oid sha256:cde761051241cba1e7f8466d71602abdb130677de55602fe6afec4b287c75b9d |
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size 2533521 |
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