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Use memory allocator in t4 bitreader

pull/1457/head
Brian Popow 6 years ago
parent
3ff41c657c
commit
769f601fa2
3 changed files with 46 additions and 30 deletions
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  1. 66
      src/ImageSharp/Formats/Tiff/Compression/T4BitReader.cs
  2. 7
      src/ImageSharp/Formats/Tiff/Compression/T4TiffCompression.cs
  3. 3
      src/ImageSharp/Formats/Tiff/README.md

66
src/ImageSharp/Formats/Tiff/Compression/T4BitReader.cs
View File

@ -2,15 +2,17 @@
// Licensed under the Apache License, Version 2.0.
using System;
using System.Buffers;
using System.IO;
using System.Linq;
using SixLabors.ImageSharp.Memory;
namespace SixLabors.ImageSharp.Formats.Tiff.Compression
{
/// <summary>
/// Bitreader for reading compressed CCITT T4 1D data.
/// </summary>
internal class T4BitReader
internal class T4BitReader : IDisposable
{
/// <summary>
/// Number of bits read.
@ -42,6 +44,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
/// </summary>
private bool isFirstScanLine;
/// <summary>
/// Indicates whether we have found a termination code which signals the end of a run.
/// </summary>
private bool terminationCodeFound;
/// <summary>
@ -49,16 +54,24 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
/// </summary>
private uint runLength;
private readonly int dataLength;
private const int MinCodeLength = 2;
private const int MaxCodeLength = 13;
public T4BitReader(Stream input, int bytesToRead)
/// <summary>
/// Initializes a new instance of the <see cref="T4BitReader" /> class.
/// </summary>
/// <param name="input">The compressed input stream.</param>
/// <param name="bytesToRead">The number of bytes to read from the stream.</param>
/// <param name="allocator">The memory allocator.</param>
public T4BitReader(Stream input, int bytesToRead, MemoryAllocator allocator)
{
// TODO: use memory allocator
this.Data = new byte[bytesToRead];
this.ReadImageDataFromStream(input, bytesToRead);
this.Data = allocator.Allocate<byte>(bytesToRead);
this.ReadImageDataFromStream(input, bytesToRead, allocator);
this.dataLength = bytesToRead;
this.bitsRead = 0;
this.value = 0;
this.curValueBitsRead = 0;
@ -72,7 +85,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
/// <summary>
/// Gets the compressed image data.
/// </summary>
public byte[] Data { get; }
public IMemoryOwner<byte> Data { get; }
/// <summary>
/// Gets a value indicating whether there is more data to read left.
@ -81,7 +94,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
{
get
{
return this.position < (ulong)this.Data.Length - 1;
return this.position < (ulong)this.dataLength - 1;
}
}
@ -207,6 +220,12 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
this.isFirstScanLine = false;
}
/// <inheritdoc/>
public void Dispose()
{
this.Data.Dispose();
}
private uint WhiteTerminatingCodeRunLength()
{
switch (this.curValueBitsRead)
@ -401,6 +420,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
case 0x2:
return 3;
}
break;
}
@ -959,31 +979,31 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
{
case 2:
{
uint[] codes = {0x3, 0x2};
uint[] codes = { 0x3, 0x2 };
return codes.Contains(this.value);
}
case 3:
{
uint[] codes = {0x02, 0x03};
uint[] codes = { 0x02, 0x03 };
return codes.Contains(this.value);
}
case 4:
{
uint[] codes = {0x03, 0x02};
uint[] codes = { 0x03, 0x02 };
return codes.Contains(this.value);
}
case 5:
{
uint[] codes = {0x03};
uint[] codes = { 0x03 };
return codes.Contains(this.value);
}
case 6:
{
uint[] codes = {0x5, 0x4};
uint[] codes = { 0x5, 0x4 };
return codes.Contains(this.value);
}
@ -1067,8 +1087,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
this.LoadNewByte();
}
Span<byte> dataSpan = this.Data.GetSpan();
int shift = 8 - this.bitsRead - 1;
var bit = (uint)((this.Data[this.position] & (1 << shift)) != 0 ? 1 : 0);
var bit = (uint)((dataSpan[(int)this.position] & (1 << shift)) != 0 ? 1 : 0);
this.bitsRead++;
return bit;
@ -1079,24 +1100,23 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
this.position++;
this.bitsRead = 0;
if (this.position >= (ulong)this.Data.Length)
if (this.position >= (ulong)this.dataLength)
{
TiffThrowHelper.ThrowImageFormatException("tiff image has invalid t4 compressed data");
}
}
private void ReadImageDataFromStream(Stream input, int bytesToRead)
private void ReadImageDataFromStream(Stream input, int bytesToRead, MemoryAllocator allocator)
{
var buffer = new byte[4096];
Span<byte> bufferSpan = buffer.AsSpan();
Span<byte> dataSpan = this.Data.AsSpan();
int bufferLength = 4096;
IMemoryOwner<byte> buffer = allocator.Allocate<byte>(bufferLength);
Span<byte> bufferSpan = buffer.GetSpan();
Span<byte> dataSpan = this.Data.GetSpan();
int read;
while (bytesToRead > 0 &&
(read = input.Read(buffer, 0, Math.Min(bufferSpan.Length, bytesToRead))) > 0)
while (bytesToRead > 0 && (read = input.Read(bufferSpan, 0, Math.Min(bufferLength, bytesToRead))) > 0)
{
buffer.AsSpan(0, read).CopyTo(dataSpan);
buffer.Slice(0, read).CopyTo(dataSpan);
bytesToRead -= read;
dataSpan = dataSpan.Slice(read);
}
@ -1106,5 +1126,5 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
TiffThrowHelper.ThrowImageFormatException("tiff image file has insufficient data");
}
}
}
}
}

7
src/ImageSharp/Formats/Tiff/Compression/T4TiffCompression.cs
View File

@ -29,10 +29,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
int whiteValue = isWhiteZero ? 0 : 1;
int blackValue = isWhiteZero ? 1 : 0;
var bitReader = new T4BitReader(stream, byteCount);
using var bitReader = new T4BitReader(stream, byteCount, this.Allocator);
uint bitsWritten = 0;
uint pixels = 0;
while (bitReader.HasMoreData)
{
bitReader.ReadNextRun();
@ -54,17 +53,13 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
{
this.WriteBits(buffer, (int)bitsWritten, bitReader.RunLength, whiteValue);
bitsWritten += bitReader.RunLength;
pixels += bitReader.RunLength;
}
else
{
this.WriteBits(buffer, (int)bitsWritten, bitReader.RunLength, blackValue);
bitsWritten += bitReader.RunLength;
pixels += bitReader.RunLength;
}
}
int foo = 0;
}
private void WriteBits(Span<byte> buffer, int pos, uint count, int value)

3
src/ImageSharp/Formats/Tiff/README.md
View File

@ -10,6 +10,7 @@
- [TIFF/EP Extension (Wikipedia)](https://en.wikipedia.org/wiki/TIFF/EP)
- [Adobe TIFF Pages](http://partners.adobe.com/public/developer/tiff/index.html)
- [Unofficial TIFF FAQ](http://www.awaresystems.be/imaging/tiff/faq.html)
- [CCITT T.4 Compression](https://www.itu.int/rec/T-REC-T.4-198811-S/_page.print)
- DNG
- [Adobe DNG Pages](https://helpx.adobe.com/photoshop/digital-negative.html)
@ -41,7 +42,7 @@
|None | | Y | |
|Ccitt1D | | | |
|PackBits | | Y | |
|CcittGroup3Fax | | | |
|CcittGroup3Fax | | Y | |
|CcittGroup4Fax | | | |
|Lzw | | Y | Based on ImageSharp GIF LZW implementation - this code could be modified to be (i) shared, or (ii) optimised for each case |
|Old Jpeg | | | |

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