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Split progressive AC method and rename GrowBufferUnsafe

af/merge-core
James Jackson-South 8 years ago
parent
86addf3a9d
commit
36081fd569
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. // The number of bits that can be read via a LUT.
public const int FastBits = 9; 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 }; 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 // LUT Bias[n] = (-1 << n) + 1
@ -22,8 +22,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
private readonly DoubleBufferedStreamReader stream; private readonly DoubleBufferedStreamReader stream;
private readonly PdfJsFrameComponent[] components; private readonly PdfJsFrameComponent[] components;
private readonly ZigZag dctZigZag; private readonly ZigZag dctZigZag;
// The restart interval.
private readonly int restartInterval; private readonly int restartInterval;
// The current component index.
private readonly int componentIndex; private readonly int componentIndex;
// The number of interleaved components.
private readonly int componentsLength; private readonly int componentsLength;
// The spectral selection start. // The spectral selection start.
@ -53,7 +59,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// The current, if any, marker in the input stream. // The current, if any, marker in the input stream.
private byte marker; 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; private bool badMarker;
// The opening position of an identified marker. // The opening position of an identified marker.
@ -68,15 +74,15 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
/// <summary> /// <summary>
/// Initializes a new instance of the <see cref="ScanDecoder"/> class. /// Initializes a new instance of the <see cref="ScanDecoder"/> class.
/// </summary> /// </summary>
/// <param name="stream">The input stream</param> /// <param name="stream">The input stream.</param>
/// <param name="components">The scan components</param> /// <param name="components">The scan components.</param>
/// <param name="componentIndex">The component index within the array</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="componentsLength">The length of the components. Different to the array length.</param>
/// <param name="restartInterval">The reset interval</param> /// <param name="restartInterval">The reset interval.</param>
/// <param name="spectralStart">The spectral selection start</param> /// <param name="spectralStart">The spectral selection start.</param>
/// <param name="spectralEnd">The spectral selection end</param> /// <param name="spectralEnd">The spectral selection end.</param>
/// <param name="successiveHigh">The successive approximation bit high end</param> /// <param name="successiveHigh">The successive approximation bit high end.</param>
/// <param name="successiveLow">The successive approximation bit low end</param> /// <param name="successiveLow">The successive approximation bit low end.</param>
public ScanDecoder( public ScanDecoder(
DoubleBufferedStreamReader stream, DoubleBufferedStreamReader stream,
PdfJsFrameComponent[] components, PdfJsFrameComponent[] components,
@ -174,7 +180,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{ {
if (this.codeBits < 24) if (this.codeBits < 24)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
// If it's NOT a restart, then just bail, so we get corrupt data // 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) if (this.codeBits < 24)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
// If it's NOT a restart, then just bail, so we get corrupt data // 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) if (this.codeBits < 24)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
// If it's NOT a restart, then just bail, so we get corrupt data // 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) if (this.codeBits < 24)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
// If it's NOT a restart, then just bail, so we get corrupt data // 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 PdfJsHuffmanTable acTable,
ref short fastACRef) ref short fastACRef)
{ {
int k;
if (this.spectralStart == 0) if (this.spectralStart == 0)
{ {
throw new ImageFormatException("Can't merge DC and AC."); throw new ImageFormatException("Can't merge DC and AC.");
@ -511,6 +515,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
if (this.successiveHigh == 0) if (this.successiveHigh == 0)
{ {
// MCU decoding for AC initial scan (either spectral selection,
// or first pass of successive approximation).
int shift = this.successiveLow; int shift = this.successiveLow;
if (this.eobrun != 0) if (this.eobrun != 0)
@ -519,7 +525,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
return; return;
} }
k = this.spectralStart; int k = this.spectralStart;
do do
{ {
int zig; int zig;
@ -582,117 +588,125 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
else else
{ {
// Refinement scan for these AC coefficients // 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--; ref short p = ref Unsafe.Add(ref blockDataRef, this.dctZigZag[k]);
for (k = this.spectralStart; k <= this.spectralEnd; k++) if (p != 0)
{ {
ref short p = ref Unsafe.Add(ref blockDataRef, this.dctZigZag[k]); if (this.GetBit() != 0)
if (p != 0)
{ {
if (this.GetBit() != 0) if ((p & bit) == 0)
{ {
if ((p & bit) == 0) if (p > 0)
{ {
if (p > 0) p += bit;
{ }
p += bit; else
} {
else p -= bit;
{
p -= bit;
}
} }
} }
} }
} }
} }
else }
else
{
k = this.spectralStart;
do
{ {
k = this.spectralStart; int rs = this.DecodeHuffman(ref acTable);
do if (rs < 0)
{ {
int rs = this.DecodeHuffman(ref acTable); throw new ImageFormatException("Bad Huffman code.");
if (rs < 0) }
{
throw new ImageFormatException("Bad Huffman code.");
}
int s = rs & 15; int s = rs & 15;
int r = rs >> 4; 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 this.eobrun = (1 << r) - 1;
// a run of 15 0s and then write s (which is 0),
// so we don't have to do anything special here if (r != 0)
if (r < 15)
{ {
this.eobrun = (1 << r) - 1; this.eobrun += this.GetBits(r);
}
if (r != 0) r = 64; // Force end of block
{ }
this.eobrun += this.GetBits(r); }
} 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 else
{ {
if (s != 1) s = -bit;
{
throw new ImageFormatException("Bad Huffman code.");
}
// Sign bit
if (this.GetBit() != 0)
{
s = bit;
}
else
{
s = -bit;
}
} }
}
// Advance by r // Advance by r
while (k <= this.spectralEnd) 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 (this.GetBit() != 0)
if (p != 0)
{ {
if (this.GetBit() != 0) if ((p & bit) == 0)
{ {
if ((p & bit) == 0) if (p > 0)
{
p += bit;
}
else
{ {
if (p > 0) p -= bit;
{
p += bit;
}
else
{
p -= bit;
}
} }
} }
} }
else }
else
{
if (r == 0)
{ {
if (r == 0) p = (short)s;
{ break;
p = (short)s;
break;
}
r--;
} }
r--;
} }
} }
while (k <= this.spectralEnd);
} }
while (k <= this.spectralEnd);
} }
} }
@ -701,7 +715,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{ {
if (this.codeBits < n) if (this.codeBits < n)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
uint k = LRot(this.codeBuffer, n); uint k = LRot(this.codeBuffer, n);
@ -716,7 +730,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{ {
if (this.codeBits < 1) if (this.codeBits < 1)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
uint k = this.codeBuffer; uint k = this.codeBuffer;
@ -727,18 +741,23 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
} }
[MethodImpl(MethodImplOptions.NoInlining)] [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 do
{ {
int b = this.nomore ? 0 : this.stream.ReadByte(); int b = this.nomore ? 0 : this.stream.ReadByte();
if (b == -1) 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; this.eof = true;
b = 0; b = 0;
} }
// Found a marker.
if (b == JpegConstants.Markers.XFF) if (b == JpegConstants.Markers.XFF)
{ {
this.markerPosition = this.stream.Position - 1; this.markerPosition = this.stream.Position - 1;
@ -844,7 +863,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{ {
if (this.codeBits < n) if (this.codeBits < n)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
int sgn = (int)this.codeBuffer >> 31; int sgn = (int)this.codeBuffer >> 31;
@ -860,7 +879,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{ {
if (this.codeBits < 16) if (this.codeBits < 16)
{ {
this.GrowBufferUnsafe(); this.FillBuffer();
} }
} }

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