/// <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>
/// 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
}
}