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Split progressive AC method and rename GrowBufferUnsafe

pull/643/head
James Jackson-South 8 years ago
parent
43c818fec2
commit
1e493ab80e
1 changed files with 117 additions and 98 deletions
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  1. 215
      src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/ScanDecoder.cs

215
src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/ScanDecoder.cs
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@ -13,7 +13,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// The number of bits that can be read via a LUT.
public const int FastBits = 9;
// LUT Bmask[n] = (1 << n) - 1
// LUT mask for n rightmost bits. Bmask[n] = (1 << n) - 1
private static readonly uint[] Bmask = { 0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767, 65535 };
// LUT Bias[n] = (-1 << n) + 1
@ -22,8 +22,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
private readonly DoubleBufferedStreamReader stream;
private readonly PdfJsFrameComponent[] components;
private readonly ZigZag dctZigZag;
// The restart interval.
private readonly int restartInterval;
// The current component index.
private readonly int componentIndex;
// The number of interleaved components.
private readonly int componentsLength;
// The spectral selection start.
@ -53,7 +59,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// The current, if any, marker in the input stream.
private byte marker;
// Whether we have a bad marker, ie. one that is not between RST0 and RST7
// Whether we have a bad marker, I.E. One that is not between RST0 and RST7
private bool badMarker;
// The opening position of an identified marker.
@ -68,15 +74,15 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
/// <summary>
/// Initializes a new instance of the <see cref="ScanDecoder"/> class.
/// </summary>
/// <param name="stream">The input stream</param>
/// <param name="components">The scan components</param>
/// <param name="componentIndex">The component index within the array</param>
/// <param name="componentsLength">The length of the components. Different to the array length</param>
/// <param name="restartInterval">The reset interval</param>
/// <param name="spectralStart">The spectral selection start</param>
/// <param name="spectralEnd">The spectral selection end</param>
/// <param name="successiveHigh">The successive approximation bit high end</param>
/// <param name="successiveLow">The successive approximation bit low end</param>
/// <param name="stream">The input stream.</param>
/// <param name="components">The scan components.</param>
/// <param name="componentIndex">The component index within the array.</param>
/// <param name="componentsLength">The length of the components. Different to the array length.</param>
/// <param name="restartInterval">The reset interval.</param>
/// <param name="spectralStart">The spectral selection start.</param>
/// <param name="spectralEnd">The spectral selection end.</param>
/// <param name="successiveHigh">The successive approximation bit high end.</param>
/// <param name="successiveLow">The successive approximation bit low end.</param>
public ScanDecoder(
DoubleBufferedStreamReader stream,
PdfJsFrameComponent[] components,
@ -174,7 +180,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < 24)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
// If it's NOT a restart, then just bail, so we get corrupt data
@ -238,7 +244,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < 24)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
// If it's NOT a restart, then just bail, so we get corrupt data
@ -309,7 +315,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < 24)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
// If it's NOT a restart, then just bail, so we get corrupt data
@ -371,7 +377,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < 24)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
// If it's NOT a restart, then just bail, so we get corrupt data
@ -502,8 +508,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
ref PdfJsHuffmanTable acTable,
ref short fastACRef)
{
int k;
if (this.spectralStart == 0)
{
throw new ImageFormatException("Can't merge DC and AC.");
@ -511,6 +515,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
if (this.successiveHigh == 0)
{
// MCU decoding for AC initial scan (either spectral selection,
// or first pass of successive approximation).
int shift = this.successiveLow;
if (this.eobrun != 0)
@ -519,7 +525,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
return;
}
k = this.spectralStart;
int k = this.spectralStart;
do
{
int zig;
@ -582,117 +588,125 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
else
{
// Refinement scan for these AC coefficients
short bit = (short)(1 << this.successiveLow);
this.DecodeBlockProgressiveACRefined(ref blockDataRef, ref acTable);
}
}
if (this.eobrun != 0)
private void DecodeBlockProgressiveACRefined(ref short blockDataRef, ref PdfJsHuffmanTable acTable)
{
int k;
// Refinement scan for these AC coefficients
short bit = (short)(1 << this.successiveLow);
if (this.eobrun != 0)
{
this.eobrun--;
for (k = this.spectralStart; k <= this.spectralEnd; k++)
{
this.eobrun--;
for (k = this.spectralStart; k <= this.spectralEnd; k++)
ref short p = ref Unsafe.Add(ref blockDataRef, this.dctZigZag[k]);
if (p != 0)
{
ref short p = ref Unsafe.Add(ref blockDataRef, this.dctZigZag[k]);
if (p != 0)
if (this.GetBit() != 0)
{
if (this.GetBit() != 0)
if ((p & bit) == 0)
{
if ((p & bit) == 0)
if (p > 0)
{
if (p > 0)
{
p += bit;
}
else
{
p -= bit;
}
p += bit;
}
else
{
p -= bit;
}
}
}
}
}
else
}
else
{
k = this.spectralStart;
do
{
k = this.spectralStart;
do
int rs = this.DecodeHuffman(ref acTable);
if (rs < 0)
{
int rs = this.DecodeHuffman(ref acTable);
if (rs < 0)
{
throw new ImageFormatException("Bad Huffman code.");
}
throw new ImageFormatException("Bad Huffman code.");
}
int s = rs & 15;
int r = rs >> 4;
int s = rs & 15;
int r = rs >> 4;
if (s == 0)
if (s == 0)
{
// r=15 s=0 should write 16 0s, so we just do
// a run of 15 0s and then write s (which is 0),
// so we don't have to do anything special here
if (r < 15)
{
// r=15 s=0 should write 16 0s, so we just do
// a run of 15 0s and then write s (which is 0),
// so we don't have to do anything special here
if (r < 15)
this.eobrun = (1 << r) - 1;
if (r != 0)
{
this.eobrun = (1 << r) - 1;
this.eobrun += this.GetBits(r);
}
if (r != 0)
{
this.eobrun += this.GetBits(r);
}
r = 64; // Force end of block
}
}
else
{
if (s != 1)
{
throw new ImageFormatException("Bad Huffman code.");
}
r = 64; // Force end of block
}
// Sign bit
if (this.GetBit() != 0)
{
s = bit;
}
else
{
if (s != 1)
{
throw new ImageFormatException("Bad Huffman code.");
}
// Sign bit
if (this.GetBit() != 0)
{
s = bit;
}
else
{
s = -bit;
}
s = -bit;
}
}
// Advance by r
while (k <= this.spectralEnd)
// Advance by r
while (k <= this.spectralEnd)
{
ref short p = ref Unsafe.Add(ref blockDataRef, this.dctZigZag[k++]);
if (p != 0)
{
ref short p = ref Unsafe.Add(ref blockDataRef, this.dctZigZag[k++]);
if (p != 0)
if (this.GetBit() != 0)
{
if (this.GetBit() != 0)
if ((p & bit) == 0)
{
if ((p & bit) == 0)
if (p > 0)
{
p += bit;
}
else
{
if (p > 0)
{
p += bit;
}
else
{
p -= bit;
}
p -= bit;
}
}
}
else
}
else
{
if (r == 0)
{
if (r == 0)
{
p = (short)s;
break;
}
r--;
p = (short)s;
break;
}
r--;
}
}
while (k <= this.spectralEnd);
}
while (k <= this.spectralEnd);
}
}
@ -701,7 +715,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < n)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
uint k = LRot(this.codeBuffer, n);
@ -716,7 +730,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < 1)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
uint k = this.codeBuffer;
@ -727,18 +741,23 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
}
[MethodImpl(MethodImplOptions.NoInlining)]
private void GrowBufferUnsafe()
private void FillBuffer()
{
// Attempt to load at least the minimum nbumber of required bits into the buffer.
// We fail to do so only if we hit a marker or reach the end of the input stream.
do
{
int b = this.nomore ? 0 : this.stream.ReadByte();
if (b == -1)
{
// We've encountered the end of the file stream which means there's no EOI marker in the image
// or the SOS marker has the wrong dimensions set.
this.eof = true;
b = 0;
}
// Found a marker.
if (b == JpegConstants.Markers.XFF)
{
this.markerPosition = this.stream.Position - 1;
@ -844,7 +863,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < n)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
int sgn = (int)this.codeBuffer >> 31;
@ -860,7 +879,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (this.codeBits < 16)
{
this.GrowBufferUnsafe();
this.FillBuffer();
}
}

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