public void Init()
{
this.WidthInBlocks = (int)MathF.Ceiling(
MathF.Ceiling(this.Frame.SamplesPerLine / 8F) * this.HorizontalSamplingFactor / this.Frame.MaxHorizontalFactor);
this.HeightInBlocks = (int)MathF.Ceiling(
MathF.Ceiling(this.Frame.Scanlines / 8F) * this.VerticalSamplingFactor / this.Frame.MaxVerticalFactor);
int blocksPerLineForMcu = this.Frame.McusPerLine * this.HorizontalSamplingFactor;
int blocksPerColumnForMcu = this.Frame.McusPerColumn * this.VerticalSamplingFactor;
this.SizeInBlocks = new Size(blocksPerLineForMcu, blocksPerColumnForMcu);
// For 4-component images (either CMYK or YCbCrK), we only support two
// hv vectors: [0x11 0x11 0x11 0x11] and [0x22 0x11 0x11 0x22].
// Theoretically, 4-component JPEG images could mix and match hv values
// but in practice, those two combinations are the only ones in use,
// and it simplifies the applyBlack code below if we can assume that:
// - for CMYK, the C and K channels have full samples, and if the M
// and Y channels subsample, they subsample both horizontally and
// vertically.
// - for YCbCrK, the Y and K channels have full samples.
if (this.Index == 0 || this.Index == 3)
{
this.SubSamplingDivisors = new Size(1, 1);
}
else
{
PdfJsFrameComponent c0 = this.Frame.Components[0];
this.SubSamplingDivisors = c0.SamplingFactors.DivideBy(this.SamplingFactors);
}
this.SpectralBlocks = this.memoryManager.Allocate2D <Block8x8>(blocksPerColumnForMcu, blocksPerLineForMcu + 1, true);
}
/// <summary>
/// Allocates the frame component blocks
/// </summary>
public void InitComponents()
{
this.McusPerLine = (int)MathF.Ceiling(this.SamplesPerLine / 8F / this.MaxHorizontalFactor);
this.McusPerColumn = (int)MathF.Ceiling(this.Scanlines / 8F / this.MaxVerticalFactor);
for (int i = 0; i < this.ComponentCount; i++)
{
PdfJsFrameComponent component = this.Components[i];
component.Init();
}
}
private void DecodeScanBaseline(
PdfJsHuffmanTables dcHuffmanTables,
PdfJsHuffmanTables acHuffmanTables,
PdfJsFrameComponent[] components,
int componentsLength,
DoubleBufferedStreamReader stream)
{
if (componentsLength == 1)
{
PdfJsFrameComponent component = components[this.compIndex];
ref short blockDataRef = ref MemoryMarshal.GetReference(MemoryMarshal.Cast <Block8x8, short>(component.SpectralBlocks.Span));
ref PdfJsHuffmanTable dcHuffmanTable = ref dcHuffmanTables[component.DCHuffmanTableId];
private void DecodeScanBaseline(
PdfJsHuffmanTables dcHuffmanTables,
PdfJsHuffmanTables acHuffmanTables,
PdfJsFrameComponent[] components,
int componentsLength,
int mcusPerLine,
int mcuToRead,
ref int mcu,
Stream stream)
{
if (componentsLength == 1)
{
PdfJsFrameComponent component = components[this.compIndex];
ref PdfJsHuffmanTable dcHuffmanTable = ref dcHuffmanTables[component.DCHuffmanTableId];
ref PdfJsHuffmanTable acHuffmanTable = ref acHuffmanTables[component.ACHuffmanTableId];
private void ParseBaselineDataInterleaved()
{
// Interleaved
int mcu = 0;
int mcusPerColumn = this.frame.McusPerColumn;
int mcusPerLine = this.frame.McusPerLine;
for (int j = 0; j < mcusPerColumn; j++)
{
for (int i = 0; i < mcusPerLine; i++)
{
// Scan an interleaved mcu... process components in order
for (int k = 0; k < this.componentsLength; k++)
{
PdfJsFrameComponent component = this.components[k];
ref PdfJsHuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
ref PdfJsHuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
ref short fastACRef = ref this.fastACTables.GetAcTableReference(component);
int h = component.HorizontalSamplingFactor;
int v = component.VerticalSamplingFactor;
// Scan out an mcu's worth of this component; that's just determined
// by the basic H and V specified for the component
for (int y = 0; y < v; y++)
{
for (int x = 0; x < h; x++)
{
if (this.eof)
{
return;
}
int mcuRow = mcu / mcusPerLine;
int mcuCol = mcu % mcusPerLine;
int blockRow = (mcuRow * v) + y;
int blockCol = (mcuCol * h) + x;
this.DecodeBlockBaseline(
component,
blockRow,
blockCol,
ref dcHuffmanTable,
ref acHuffmanTable,
ref fastACRef);
}
}
}
/// <summary>
/// Decodes the spectral scan
/// </summary>
/// <param name="frame">The image frame</param>
/// <param name="stream">The input stream</param>
/// <param name="dcHuffmanTables">The DC Huffman tables</param>
/// <param name="acHuffmanTables">The AC Huffman tables</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="resetInterval">The reset interval</param>
/// <param name="spectralStart">The spectral selection start</param>
/// <param name="spectralEnd">The spectral selection end</param>
/// <param name="successivePrev">The successive approximation bit high end</param>
/// <param name="successive">The successive approximation bit low end</param>
public void DecodeScan(
PdfJsFrame frame,
Stream stream,
PdfJsHuffmanTables dcHuffmanTables,
PdfJsHuffmanTables acHuffmanTables,
PdfJsFrameComponent[] components,
int componentIndex,
int componentsLength,
ushort resetInterval,
int spectralStart,
int spectralEnd,
int successivePrev,
int successive)
{
this.markerBuffer = new byte[2];
this.compIndex = componentIndex;
this.specStart = spectralStart;
this.specEnd = spectralEnd;
this.successiveState = successive;
this.endOfStreamReached = false;
this.unexpectedMarkerReached = false;
bool progressive = frame.Progressive;
int mcusPerLine = frame.McusPerLine;
int mcu = 0;
int mcuExpected;
if (componentsLength == 1)
{
mcuExpected = components[this.compIndex].WidthInBlocks * components[this.compIndex].HeightInBlocks;
}
else
{
mcuExpected = mcusPerLine * frame.McusPerColumn;
}
PdfJsFileMarker fileMarker;
while (mcu < mcuExpected)
{
// Reset interval stuff
int mcuToRead = resetInterval != 0 ? Math.Min(mcuExpected - mcu, resetInterval) : mcuExpected;
for (int i = 0; i < components.Length; i++)
{
PdfJsFrameComponent c = components[i];
c.Pred = 0;
}
this.eobrun = 0;
if (!progressive)
{
this.DecodeScanBaseline(dcHuffmanTables, acHuffmanTables, components, componentsLength, mcusPerLine, mcuToRead, ref mcu, stream);
}
else
{
if (this.specStart == 0)
{
if (successivePrev == 0)
{
this.DecodeScanDCFirst(dcHuffmanTables, components, componentsLength, mcusPerLine, mcuToRead, ref mcu, stream);
}
else
{
this.DecodeScanDCSuccessive(components, componentsLength, mcusPerLine, mcuToRead, ref mcu, stream);
}
}
else
{
if (successivePrev == 0)
{
this.DecodeScanACFirst(acHuffmanTables, components, componentsLength, mcusPerLine, mcuToRead, ref mcu, stream);
}
else
{
this.DecodeScanACSuccessive(acHuffmanTables, components, componentsLength, mcusPerLine, mcuToRead, ref mcu, stream);
}
}
}
// Find marker
this.bitsCount = 0;
this.accumulator = 0;
this.bitsUnRead = 0;
fileMarker = PdfJsJpegDecoderCore.FindNextFileMarker(this.markerBuffer, stream);
// Some bad images seem to pad Scan blocks with e.g. zero bytes, skip past
// those to attempt to find a valid marker (fixes issue4090.pdf) in original code.
if (fileMarker.Invalid)
{
#if DEBUG
Debug.WriteLine($"DecodeScan - Unexpected MCU data at {stream.Position}, next marker is: {fileMarker.Marker:X}");
#endif
}
ushort marker = fileMarker.Marker;
// RSTn - We've already read the bytes and altered the position so no need to skip
if (marker >= PdfJsJpegConstants.Markers.RST0 && marker <= PdfJsJpegConstants.Markers.RST7)
{
continue;
}
if (!fileMarker.Invalid)
{
// We've found a valid marker.
// Rewind the stream to the position of the marker and break
stream.Position = fileMarker.Position;
break;
}
}
fileMarker = PdfJsJpegDecoderCore.FindNextFileMarker(this.markerBuffer, stream);
// Some images include more Scan blocks than expected, skip past those and
// attempt to find the next valid marker (fixes issue8182.pdf) in original code.
if (fileMarker.Invalid)
{
#if DEBUG
Debug.WriteLine($"DecodeScan - Unexpected MCU data at {stream.Position}, next marker is: {fileMarker.Marker:X}");
#endif
}
else
{
// We've found a valid marker.
// Rewind the stream to the position of the marker
stream.Position = fileMarker.Position;
}
}
/// <summary>
/// A port of Poppler's IDCT method which in turn is taken from:
/// Christoph Loeffler, Adriaan Ligtenberg, George S. Moschytz,
/// 'Practical Fast 1-D DCT Algorithms with 11 Multiplications',
/// IEEE Intl. Conf. on Acoustics, Speech & Signal Processing, 1989, 988-991.
/// </summary>
/// <param name="component">The fram component</param>
/// <param name="blockBufferOffset">The block buffer offset</param>
/// <param name="computationBuffer">The computational buffer for holding temp values</param>
/// <param name="quantizationTable">The quantization table</param>
public static void QuantizeAndInverse(PdfJsFrameComponent component, int blockBufferOffset, ref Span <short> computationBuffer, ref Span <short> quantizationTable)
{
Span <short> blockData = component.BlockData.Slice(blockBufferOffset);
int v0, v1, v2, v3, v4, v5, v6, v7;
int p0, p1, p2, p3, p4, p5, p6, p7;
int t;
// inverse DCT on rows
for (int row = 0; row < 64; row += 8)
{
// gather block data
p0 = blockData[row];
p1 = blockData[row + 1];
p2 = blockData[row + 2];
p3 = blockData[row + 3];
p4 = blockData[row + 4];
p5 = blockData[row + 5];
p6 = blockData[row + 6];
p7 = blockData[row + 7];
// dequant p0
p0 *= quantizationTable[row];
// check for all-zero AC coefficients
if ((p1 | p2 | p3 | p4 | p5 | p6 | p7) == 0)
{
t = ((DctSqrt2 * p0) + 512) >> 10;
short st = (short)t;
computationBuffer[row] = st;
computationBuffer[row + 1] = st;
computationBuffer[row + 2] = st;
computationBuffer[row + 3] = st;
computationBuffer[row + 4] = st;
computationBuffer[row + 5] = st;
computationBuffer[row + 6] = st;
computationBuffer[row + 7] = st;
continue;
}
// dequant p1 ... p7
p1 *= quantizationTable[row + 1];
p2 *= quantizationTable[row + 2];
p3 *= quantizationTable[row + 3];
p4 *= quantizationTable[row + 4];
p5 *= quantizationTable[row + 5];
p6 *= quantizationTable[row + 6];
p7 *= quantizationTable[row + 7];
// stage 4
v0 = ((DctSqrt2 * p0) + 128) >> 8;
v1 = ((DctSqrt2 * p4) + 128) >> 8;
v2 = p2;
v3 = p6;
v4 = ((DctSqrt1D2 * (p1 - p7)) + 128) >> 8;
v7 = ((DctSqrt1D2 * (p1 + p7)) + 128) >> 8;
v5 = p3 << 4;
v6 = p5 << 4;
// stage 3
v0 = (v0 + v1 + 1) >> 1;
v1 = v0 - v1;
t = ((v2 * DctSin6) + (v3 * DctCos6) + 128) >> 8;
v2 = ((v2 * DctCos6) - (v3 * DctSin6) + 128) >> 8;
v3 = t;
v4 = (v4 + v6 + 1) >> 1;
v6 = v4 - v6;
v7 = (v7 + v5 + 1) >> 1;
v5 = v7 - v5;
// stage 2
v0 = (v0 + v3 + 1) >> 1;
v3 = v0 - v3;
v1 = (v1 + v2 + 1) >> 1;
v2 = v1 - v2;
t = ((v4 * DctSin3) + (v7 * DctCos3) + 2048) >> 12;
v4 = ((v4 * DctCos3) - (v7 * DctSin3) + 2048) >> 12;
v7 = t;
t = ((v5 * DctSin1) + (v6 * DctCos1) + 2048) >> 12;
v5 = ((v5 * DctCos1) - (v6 * DctSin1) + 2048) >> 12;
v6 = t;
// stage 1
computationBuffer[row] = (short)(v0 + v7);
computationBuffer[row + 7] = (short)(v0 - v7);
computationBuffer[row + 1] = (short)(v1 + v6);
computationBuffer[row + 6] = (short)(v1 - v6);
computationBuffer[row + 2] = (short)(v2 + v5);
computationBuffer[row + 5] = (short)(v2 - v5);
computationBuffer[row + 3] = (short)(v3 + v4);
computationBuffer[row + 4] = (short)(v3 - v4);
}
// inverse DCT on columns
for (int col = 0; col < 8; ++col)
{
p0 = computationBuffer[col];
p1 = computationBuffer[col + 8];
p2 = computationBuffer[col + 16];
p3 = computationBuffer[col + 24];
p4 = computationBuffer[col + 32];
p5 = computationBuffer[col + 40];
p6 = computationBuffer[col + 48];
p7 = computationBuffer[col + 56];
// check for all-zero AC coefficients
if ((p1 | p2 | p3 | p4 | p5 | p6 | p7) == 0)
{
t = ((DctSqrt2 * p0) + 8192) >> 14;
// convert to 8 bit
t = (t < -2040) ? 0 : (t >= 2024) ? MaxJSample : (t + 2056) >> 4;
short st = (short)t;
blockData[col] = st;
blockData[col + 8] = st;
blockData[col + 16] = st;
blockData[col + 24] = st;
blockData[col + 32] = st;
blockData[col + 40] = st;
blockData[col + 48] = st;
blockData[col + 56] = st;
continue;
}
// stage 4
v0 = ((DctSqrt2 * p0) + 2048) >> 12;
v1 = ((DctSqrt2 * p4) + 2048) >> 12;
v2 = p2;
v3 = p6;
v4 = ((DctSqrt1D2 * (p1 - p7)) + 2048) >> 12;
v7 = ((DctSqrt1D2 * (p1 + p7)) + 2048) >> 12;
v5 = p3;
v6 = p5;
// stage 3
// Shift v0 by 128.5 << 5 here, so we don't need to shift p0...p7 when
// converting to UInt8 range later.
v0 = ((v0 + v1 + 1) >> 1) + 4112;
v1 = v0 - v1;
t = ((v2 * DctSin6) + (v3 * DctCos6) + 2048) >> 12;
v2 = ((v2 * DctCos6) - (v3 * DctSin6) + 2048) >> 12;
v3 = t;
v4 = (v4 + v6 + 1) >> 1;
v6 = v4 - v6;
v7 = (v7 + v5 + 1) >> 1;
v5 = v7 - v5;
// stage 2
v0 = (v0 + v3 + 1) >> 1;
v3 = v0 - v3;
v1 = (v1 + v2 + 1) >> 1;
v2 = v1 - v2;
t = ((v4 * DctSin3) + (v7 * DctCos3) + 2048) >> 12;
v4 = ((v4 * DctCos3) - (v7 * DctSin3) + 2048) >> 12;
v7 = t;
t = ((v5 * DctSin1) + (v6 * DctCos1) + 2048) >> 12;
v5 = ((v5 * DctCos1) - (v6 * DctSin1) + 2048) >> 12;
v6 = t;
// stage 1
p0 = v0 + v7;
p7 = v0 - v7;
p1 = v1 + v6;
p6 = v1 - v6;
p2 = v2 + v5;
p5 = v2 - v5;
p3 = v3 + v4;
p4 = v3 - v4;
// convert to 8-bit integers
p0 = (p0 < 16) ? 0 : (p0 >= 4080) ? MaxJSample : p0 >> 4;
p1 = (p1 < 16) ? 0 : (p1 >= 4080) ? MaxJSample : p1 >> 4;
p2 = (p2 < 16) ? 0 : (p2 >= 4080) ? MaxJSample : p2 >> 4;
p3 = (p3 < 16) ? 0 : (p3 >= 4080) ? MaxJSample : p3 >> 4;
p4 = (p4 < 16) ? 0 : (p4 >= 4080) ? MaxJSample : p4 >> 4;
p5 = (p5 < 16) ? 0 : (p5 >= 4080) ? MaxJSample : p5 >> 4;
p6 = (p6 < 16) ? 0 : (p6 >= 4080) ? MaxJSample : p6 >> 4;
p7 = (p7 < 16) ? 0 : (p7 >= 4080) ? MaxJSample : p7 >> 4;
// store block data
blockData[col] = (short)p0;
blockData[col + 8] = (short)p1;
blockData[col + 16] = (short)p2;
blockData[col + 24] = (short)p3;
blockData[col + 32] = (short)p4;
blockData[col + 40] = (short)p5;
blockData[col + 48] = (short)p6;
blockData[col + 56] = (short)p7;
}
}
/// <summary>
/// A port of <see href="https://github.com/libjpeg-turbo/libjpeg-turbo/blob/master/jidctfst.c#L171"/>
/// A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
/// on each row(or vice versa, but it's more convenient to emit a row at
/// a time). Direct algorithms are also available, but they are much more
/// complex and seem not to be any faster when reduced to code.
///
/// This implementation is based on Arai, Agui, and Nakajima's algorithm for
/// scaled DCT.Their original paper (Trans.IEICE E-71(11):1095) is in
/// Japanese, but the algorithm is described in the Pennebaker & Mitchell
/// JPEG textbook(see REFERENCES section in file README.ijg). The following
/// code is based directly on figure 4-8 in P&M.
/// While an 8-point DCT cannot be done in less than 11 multiplies, it is
/// possible to arrange the computation so that many of the multiplies are
/// simple scalings of the final outputs.These multiplies can then be
/// folded into the multiplications or divisions by the JPEG quantization
/// table entries. The AA&N method leaves only 5 multiplies and 29 adds
/// to be done in the DCT itself.
/// The primary disadvantage of this method is that with fixed-point math,
/// accuracy is lost due to imprecise representation of the scaled
/// quantization values.The smaller the quantization table entry, the less
/// precise the scaled value, so this implementation does worse with high -
/// quality - setting files than with low - quality ones.
/// </summary>
/// <param name="component">The frame component</param>
/// <param name="blockBufferOffset">The block buffer offset</param>
/// <param name="computationBuffer">The computational buffer for holding temp values</param>
/// <param name="multiplierTable">The multiplier table</param>
public static void QuantizeAndInverseFast(PdfJsFrameComponent component, int blockBufferOffset, ref Span <short> computationBuffer, ref Span <short> multiplierTable)
{
Span <short> blockData = component.BlockData.Slice(blockBufferOffset);
int p0, p1, p2, p3, p4, p5, p6, p7;
for (int col = 0; col < 8; col++)
{
// Gather block data
p0 = blockData[col];
p1 = blockData[col + 8];
p2 = blockData[col + 16];
p3 = blockData[col + 24];
p4 = blockData[col + 32];
p5 = blockData[col + 40];
p6 = blockData[col + 48];
p7 = blockData[col + 56];
int tmp0 = p0 * multiplierTable[col];
// Due to quantization, we will usually find that many of the input
// coefficients are zero, especially the AC terms. We can exploit this
// by short-circuiting the IDCT calculation for any column in which all
// the AC terms are zero. In that case each output is equal to the
// DC coefficient (with scale factor as needed).
// With typical images and quantization tables, half or more of the
// column DCT calculations can be simplified this way.
if ((p1 | p2 | p3 | p4 | p5 | p6 | p7) == 0)
{
short dcval = (short)tmp0;
computationBuffer[col] = dcval;
computationBuffer[col + 8] = dcval;
computationBuffer[col + 16] = dcval;
computationBuffer[col + 24] = dcval;
computationBuffer[col + 32] = dcval;
computationBuffer[col + 40] = dcval;
computationBuffer[col + 48] = dcval;
computationBuffer[col + 56] = dcval;
continue;
}
// Even part
int tmp1 = p2 * multiplierTable[col + 16];
int tmp2 = p4 * multiplierTable[col + 32];
int tmp3 = p6 * multiplierTable[col + 48];
int tmp10 = tmp0 + tmp2; // Phase 3
int tmp11 = tmp0 - tmp2;
int tmp13 = tmp1 + tmp3; // Phases 5-3
int tmp12 = Multiply(tmp1 - tmp3, FIX_1_414213562) - tmp13; // 2*c4
tmp0 = tmp10 + tmp13; // Phase 2
tmp3 = tmp10 - tmp13;
tmp1 = tmp11 + tmp12;
tmp2 = tmp11 - tmp12;
// Odd Part
int tmp4 = p1 * multiplierTable[col + 8];
int tmp5 = p3 * multiplierTable[col + 24];
int tmp6 = p5 * multiplierTable[col + 40];
int tmp7 = p7 * multiplierTable[col + 56];
int z13 = tmp6 + tmp5; // Phase 6
int z10 = tmp6 - tmp5;
int z11 = tmp4 + tmp7;
int z12 = tmp4 - tmp7;
tmp7 = z11 + z13; // Phase 5
tmp11 = Multiply(z11 - z13, FIX_1_414213562); // 2*c4
int z5 = Multiply(z10 + z12, FIX_1_847759065); // 2*c2
tmp10 = z5 - Multiply(z12, FIX_1_082392200); // 2*(c2-c6)
tmp12 = z5 - Multiply(z10, FIX_2_613125930); // 2*(c2+c6)
tmp6 = tmp12 - tmp7; // Phase 2
tmp5 = tmp11 - tmp6;
tmp4 = tmp10 - tmp5;
computationBuffer[col] = (short)(tmp0 + tmp7);
computationBuffer[col + 56] = (short)(tmp0 - tmp7);
computationBuffer[col + 8] = (short)(tmp1 + tmp6);
computationBuffer[col + 48] = (short)(tmp1 - tmp6);
computationBuffer[col + 16] = (short)(tmp2 + tmp5);
computationBuffer[col + 40] = (short)(tmp2 - tmp5);
computationBuffer[col + 24] = (short)(tmp3 + tmp4);
computationBuffer[col + 32] = (short)(tmp3 - tmp4);
}
// Pass 2: process rows from work array, store into output array.
// Note that we must descale the results by a factor of 8 == 2**3,
// and also undo the pass 1 bits scaling.
for (int row = 0; row < 64; row += 8)
{
p1 = computationBuffer[row + 1];
p2 = computationBuffer[row + 2];
p3 = computationBuffer[row + 3];
p4 = computationBuffer[row + 4];
p5 = computationBuffer[row + 5];
p6 = computationBuffer[row + 6];
p7 = computationBuffer[row + 7];
// Add range center and fudge factor for final descale and range-limit.
int z5 = computationBuffer[row] + (RangeCenter << (Pass1Bits + 3)) + (1 << (Pass1Bits + 2));
// Check for all-zero AC coefficients
if ((p1 | p2 | p3 | p4 | p5 | p6 | p7) == 0)
{
byte dcval = Limit[LimitOffset + (RightShift(z5, Pass1Bits + 3) & RangeMask)];
blockData[row] = dcval;
blockData[row + 1] = dcval;
blockData[row + 2] = dcval;
blockData[row + 3] = dcval;
blockData[row + 4] = dcval;
blockData[row + 5] = dcval;
blockData[row + 6] = dcval;
blockData[row + 7] = dcval;
continue;
}
// Even part
int tmp10 = z5 + p4;
int tmp11 = z5 - p4;
int tmp13 = p2 + p6;
int tmp12 = Multiply(p2 - p6, FIX_1_414213562) - tmp13; // 2*c4
int tmp0 = tmp10 + tmp13;
int tmp3 = tmp10 - tmp13;
int tmp1 = tmp11 + tmp12;
int tmp2 = tmp11 - tmp12;
// Odd part
int z13 = p5 + p3;
int z10 = p5 - p3;
int z11 = p1 + p7;
int z12 = p1 - p7;
int tmp7 = z11 + z13; // Phase 5
tmp11 = Multiply(z11 - z13, FIX_1_414213562); // 2*c4
z5 = Multiply(z10 + z12, FIX_1_847759065); // 2*c2
tmp10 = z5 - Multiply(z12, FIX_1_082392200); // 2*(c2-c6)
tmp12 = z5 - Multiply(z10, FIX_2_613125930); // 2*(c2+c6)
int tmp6 = tmp12 - tmp7; // Phase 2
int tmp5 = tmp11 - tmp6;
int tmp4 = tmp10 - tmp5;
// Final output stage: scale down by a factor of 8, offset, and range-limit
blockData[row] = Limit[LimitOffset + (RightShift(tmp0 + tmp7, Pass1Bits + 3) & RangeMask)];
blockData[row + 7] = Limit[LimitOffset + (RightShift(tmp0 - tmp7, Pass1Bits + 3) & RangeMask)];
blockData[row + 1] = Limit[LimitOffset + (RightShift(tmp1 + tmp6, Pass1Bits + 3) & RangeMask)];
blockData[row + 6] = Limit[LimitOffset + (RightShift(tmp1 - tmp6, Pass1Bits + 3) & RangeMask)];
blockData[row + 2] = Limit[LimitOffset + (RightShift(tmp2 + tmp5, Pass1Bits + 3) & RangeMask)];
blockData[row + 5] = Limit[LimitOffset + (RightShift(tmp2 - tmp5, Pass1Bits + 3) & RangeMask)];
blockData[row + 3] = Limit[LimitOffset + (RightShift(tmp3 + tmp4, Pass1Bits + 3) & RangeMask)];
blockData[row + 4] = Limit[LimitOffset + (RightShift(tmp3 - tmp4, Pass1Bits + 3) & RangeMask)];
}
}
/// <summary>
/// Decodes the spectral scan
/// </summary>
/// <param name="frame">The image frame</param>
/// <param name="stream">The input stream</param>
/// <param name="dcHuffmanTables">The DC Huffman tables</param>
/// <param name="acHuffmanTables">The AC Huffman tables</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="resetInterval">The reset interval</param>
/// <param name="spectralStart">The spectral selection start</param>
/// <param name="spectralEnd">The spectral selection end</param>
/// <param name="successivePrev">The successive approximation bit high end</param>
/// <param name="successive">The successive approximation bit low end</param>
public void DecodeScan(
PdfJsFrame frame,
DoubleBufferedStreamReader stream,
PdfJsHuffmanTables dcHuffmanTables,
PdfJsHuffmanTables acHuffmanTables,
PdfJsFrameComponent[] components,
int componentIndex,
int componentsLength,
ushort resetInterval,
int spectralStart,
int spectralEnd,
int successivePrev,
int successive)
{
this.dctZigZag = ZigZag.CreateUnzigTable();
this.markerBuffer = new byte[2];
this.compIndex = componentIndex;
this.specStart = spectralStart;
this.specEnd = spectralEnd;
this.successiveState = successive;
this.endOfStreamReached = false;
this.unexpectedMarkerReached = false;
bool progressive = frame.Progressive;
this.mcusPerLine = frame.McusPerLine;
this.mcu = 0;
int mcuExpected;
if (componentsLength == 1)
{
mcuExpected = components[this.compIndex].WidthInBlocks * components[this.compIndex].HeightInBlocks;
}
else
{
mcuExpected = this.mcusPerLine * frame.McusPerColumn;
}
while (this.mcu < mcuExpected)
{
// Reset interval stuff
this.mcuToRead = resetInterval != 0 ? Math.Min(mcuExpected - this.mcu, resetInterval) : mcuExpected;
for (int i = 0; i < components.Length; i++)
{
PdfJsFrameComponent c = components[i];
c.Pred = 0;
}
this.eobrun = 0;
if (!progressive)
{
this.DecodeScanBaseline(dcHuffmanTables, acHuffmanTables, components, componentsLength, stream);
}
else
{
bool isAc = this.specStart != 0;
bool isFirst = successivePrev == 0;
PdfJsHuffmanTables huffmanTables = isAc ? acHuffmanTables : dcHuffmanTables;
this.DecodeScanProgressive(huffmanTables, isAc, isFirst, components, componentsLength, stream);
}
// Reset
// TODO: I do not understand why these values are reset? We should surely be tracking the bits across mcu's?
this.bitsCount = 0;
this.bitsData = 0;
this.unexpectedMarkerReached = false;
// Some images include more scan blocks than expected, skip past those and
// attempt to find the next valid marker
PdfJsFileMarker fileMarker = PdfJsJpegDecoderCore.FindNextFileMarker(this.markerBuffer, stream);
byte marker = fileMarker.Marker;
// RSTn - We've already read the bytes and altered the position so no need to skip
if (marker >= PdfJsJpegConstants.Markers.RST0 && marker <= PdfJsJpegConstants.Markers.RST7)
{
continue;
}
if (!fileMarker.Invalid)
{
// We've found a valid marker.
// Rewind the stream to the position of the marker and break
stream.Position = fileMarker.Position;
break;
}
#if DEBUG
Debug.WriteLine($"DecodeScan - Unexpected MCU data at {stream.Position}, next marker is: {fileMarker.Marker:X}");
#endif
}
}
public ref short GetAcTableReference(PdfJsFrameComponent component)
{
return(ref this.tables.GetRowSpan(component.ACHuffmanTableId)[0]);
}