public static bool TryParse(ReadOnlySequence <byte> buffer, bool metadataOnly, out JpegScanHeader scanHeader, out int bytesConsumed)
{
if (buffer.IsSingleSegment)
{
return(TryParse(buffer.First.Span, metadataOnly, out scanHeader, out bytesConsumed));
}
bytesConsumed = 0;
if (buffer.IsEmpty)
{
scanHeader = default;
return(false);
}
byte numberOfComponents = buffer.First.Span[0];
buffer = buffer.Slice(1);
bytesConsumed++;
if (buffer.Length < (2 * numberOfComponents + 3))
{
scanHeader = default;
return(false);
}
JpegScanComponentSpecificationParameters[]? components;
if (metadataOnly)
{
components = null;
buffer = buffer.Slice(2 * numberOfComponents);
bytesConsumed += 2 * numberOfComponents;
}
else
{
components = new JpegScanComponentSpecificationParameters[numberOfComponents];
for (int i = 0; i < components.Length; i++)
{
#pragma warning disable CA1806
JpegScanComponentSpecificationParameters.TryParse(buffer, out components[i]);
#pragma warning restore CA1806
buffer = buffer.Slice(2);
bytesConsumed += 2;
}
}
Span <byte> local = stackalloc byte[4];
buffer.Slice(0, 3).CopyTo(local);
byte successiveApproximationBitPosition = local[2];
byte endOfSpectralSelection = local[1];
byte startOfSpectralSelection = local[0];
bytesConsumed += 3;
scanHeader = new JpegScanHeader(numberOfComponents, components, startOfSpectralSelection, endOfSpectralSelection, (byte)(successiveApproximationBitPosition >> 4), (byte)(successiveApproximationBitPosition & 0xf));
return(true);
}
private JpegScanHeader ProcessScanHeader(ref JpegReader reader, bool metadataOnly)
{
if (!reader.TryReadLength(out ushort length))
{
ThrowInvalidDataException(reader.ConsumedByteCount, "Unexpected end of input data when reading segment length.");
}
if (!reader.TryReadBytes(length, out ReadOnlySequence <byte> buffer))
{
ThrowInvalidDataException(reader.ConsumedByteCount, "Unexpected end of input data when reading segment content.");
}
if (!JpegScanHeader.TryParse(buffer, metadataOnly, out JpegScanHeader scanHeader, out int bytesConsumed))
{
ThrowInvalidDataException(reader.ConsumedByteCount - length + bytesConsumed, "Failed to parse scan header.");
}
return(scanHeader);
}
private void CopyScanBaseline(ref JpegReader reader, ref JpegWriter writer, JpegScanHeader scanHeader)
{
JpegFrameHeader frameHeader = _frameHeader.GetValueOrDefault();
if (scanHeader.Components is null)
{
throw new InvalidOperationException();
}
// Compute maximum sampling factor
byte maxHorizontalSampling = 1;
byte maxVerticalSampling = 1;
foreach (JpegFrameComponentSpecificationParameters currentFrameComponent in frameHeader.Components !)
{
maxHorizontalSampling = Math.Max(maxHorizontalSampling, currentFrameComponent.HorizontalSamplingFactor);
maxVerticalSampling = Math.Max(maxVerticalSampling, currentFrameComponent.VerticalSamplingFactor);
}
// Resolve each component
JpegTranscodeComponent[] components = new JpegTranscodeComponent[scanHeader.NumberOfComponents];
for (int i = 0; i < scanHeader.NumberOfComponents; i++)
{
JpegScanComponentSpecificationParameters scanComponenet = scanHeader.Components[i];
int componentIndex = 0;
JpegFrameComponentSpecificationParameters?frameComponent = null;
for (int j = 0; j < frameHeader.NumberOfComponents; j++)
{
JpegFrameComponentSpecificationParameters currentFrameComponent = frameHeader.Components[j];
if (scanComponenet.ScanComponentSelector == currentFrameComponent.Identifier)
{
componentIndex = j;
frameComponent = currentFrameComponent;
}
}
if (frameComponent is null)
{
throw new InvalidDataException();
}
components[i] = new JpegTranscodeComponent
{
ComponentIndex = componentIndex,
HorizontalSamplingFactor = frameComponent.GetValueOrDefault().HorizontalSamplingFactor,
VerticalSamplingFactor = frameComponent.GetValueOrDefault().VerticalSamplingFactor,
DcTable = GetHuffmanTable(true, scanComponenet.DcEntropyCodingTableSelector),
AcTable = GetHuffmanTable(false, scanComponenet.AcEntropyCodingTableSelector),
DcEncodingTable = _encodingTables.GetTable(true, scanComponenet.DcEntropyCodingTableSelector),
AcEncodingTable = _encodingTables.GetTable(false, scanComponenet.AcEntropyCodingTableSelector)
};
}
// Prepare
int mcusPerLine = (frameHeader.SamplesPerLine + 8 * maxHorizontalSampling - 1) / (8 * maxHorizontalSampling);
int mcusPerColumn = (frameHeader.NumberOfLines + 8 * maxVerticalSampling - 1) / (8 * maxVerticalSampling);
JpegBitReader bitReader = new JpegBitReader(reader.RemainingBytes);
int mcusBeforeRestart = _restartInterval;
bool eoiReached = false;
writer.EnterBitMode();
for (int rowMcu = 0; rowMcu < mcusPerColumn && !eoiReached; rowMcu++)
{
for (int colMcu = 0; colMcu < mcusPerLine && !eoiReached; colMcu++)
{
foreach (JpegTranscodeComponent component in components)
{
int h = component.HorizontalSamplingFactor;
int v = component.VerticalSamplingFactor;
for (int y = 0; y < v; y++)
{
for (int x = 0; x < h; x++)
{
CopyBlockBaseline(ref bitReader, ref writer, component);
}
}
}
if (_restartInterval > 0 && (--mcusBeforeRestart) == 0)
{
bitReader.AdvanceAlignByte();
JpegMarker marker = bitReader.TryReadMarker();
if (marker == JpegMarker.EndOfImage)
{
eoiReached = true;
break;
}
if (!marker.IsRestartMarker())
{
throw new InvalidOperationException("Expect restart marker.");
}
mcusBeforeRestart = _restartInterval;
writer.ExitBitMode();
writer.WriteMarker(marker);
writer.EnterBitMode();
}
}
}
bitReader.AdvanceAlignByte();
writer.ExitBitMode();
int bytesConsumed = reader.RemainingByteCount - bitReader.RemainingBits / 8;
if (eoiReached)
{
bytesConsumed -= 2;
}
else if (bitReader.TryPeekMarker() != 0)
{
if (!bitReader.TryPeekMarker().IsRestartMarker())
{
bytesConsumed -= 2;
}
}
reader.TryAdvance(bytesConsumed);
}
public void Scan()
{
if (_inputBuffer.IsEmpty)
{
throw new InvalidOperationException("Input buffer is not specified.");
}
JpegReader reader = new JpegReader(_inputBuffer);
// Reset frame header
_frameHeader = default;
bool scanRead = false;
bool endOfImageReached = false;
while (!endOfImageReached && !reader.IsEmpty)
{
// Read next marker
if (!reader.TryReadMarker(out JpegMarker marker))
{
ThrowInvalidDataException(reader.ConsumedByteCount, "No marker found.");
return;
}
switch (marker)
{
case JpegMarker.StartOfImage:
break;
case JpegMarker.StartOfFrame0:
ProcessFrameHeader(ref reader, false, false);
break;
case JpegMarker.StartOfFrame1:
ProcessFrameHeader(ref reader, false, false);
break;
case JpegMarker.StartOfFrame3:
case JpegMarker.StartOfFrame5:
case JpegMarker.StartOfFrame6:
case JpegMarker.StartOfFrame7:
case JpegMarker.StartOfFrame9:
case JpegMarker.StartOfFrame10:
case JpegMarker.StartOfFrame11:
case JpegMarker.StartOfFrame13:
case JpegMarker.StartOfFrame14:
case JpegMarker.StartOfFrame15:
ThrowInvalidDataException(reader.ConsumedByteCount, $"This type of JPEG stream is not supported ({marker}).");
return;
case JpegMarker.DefineHuffmanTable:
ProcessDefineHuffmanTable(ref reader);
break;
case JpegMarker.DefineQuantizationTable:
ProcessDefineQuantizationTable(ref reader);
break;
case JpegMarker.DefineRestartInterval:
ProcessDefineRestartInterval(ref reader);
break;
case JpegMarker.StartOfScan:
JpegScanHeader scanHeader = ProcessScanHeader(ref reader, false);
ProcessScanBaseline(ref reader, scanHeader);
scanRead = true;
break;
case JpegMarker.DefineRestart0:
case JpegMarker.DefineRestart1:
case JpegMarker.DefineRestart2:
case JpegMarker.DefineRestart3:
case JpegMarker.DefineRestart4:
case JpegMarker.DefineRestart5:
case JpegMarker.DefineRestart6:
case JpegMarker.DefineRestart7:
break;
case JpegMarker.EndOfImage:
endOfImageReached = true;
break;
default:
ProcessOtherMarker(ref reader);
break;
}
}
if (!scanRead)
{
ThrowInvalidDataException(reader.ConsumedByteCount, "No image data is read.");
return;
}
}
public void Optimize(bool strip = true)
{
if (_encodingTables.IsEmpty)
{
throw new InvalidOperationException();
}
IBufferWriter <byte> bufferWriter = _output ?? throw new InvalidOperationException();
JpegReader reader = new JpegReader(_inputBuffer);
var writer = new JpegWriter(bufferWriter, _minimumBufferSegmentSize);
bool eoiReached = false;
bool huffmanTableWritten = false;
bool quantizationTableWritten = false;
while (!eoiReached && !reader.IsEmpty)
{
if (!reader.TryReadMarker(out JpegMarker marker))
{
ThrowInvalidDataException(reader.ConsumedByteCount, "No marker found.");
return;
}
switch (marker)
{
case JpegMarker.StartOfImage:
writer.WriteMarker(marker);
break;
case JpegMarker.App0:
case JpegMarker.StartOfFrame0:
case JpegMarker.StartOfFrame1:
writer.WriteMarker(marker);
CopyMarkerData(ref reader, ref writer);
break;
case JpegMarker.StartOfFrame2:
ProcessFrameHeader(ref reader, false, true);
throw new InvalidDataException("Progressive JPEG is not supported currently.");
case JpegMarker.StartOfFrame3:
case JpegMarker.StartOfFrame5:
case JpegMarker.StartOfFrame6:
case JpegMarker.StartOfFrame7:
case JpegMarker.StartOfFrame9:
case JpegMarker.StartOfFrame10:
case JpegMarker.StartOfFrame11:
case JpegMarker.StartOfFrame13:
case JpegMarker.StartOfFrame14:
case JpegMarker.StartOfFrame15:
ThrowInvalidDataException(reader.ConsumedByteCount, $"This type of JPEG stream is not supported ({marker}).");
return;
case JpegMarker.DefineHuffmanTable:
if (!huffmanTableWritten)
{
WriteHuffmanTables(ref writer);
huffmanTableWritten = true;
}
break;
case JpegMarker.DefineQuantizationTable:
if (!quantizationTableWritten)
{
WriteQuantizationTables(ref writer);
quantizationTableWritten = true;
}
break;
case JpegMarker.StartOfScan:
writer.WriteMarker(marker);
ReadOnlySequence <byte> buffer = CopyMarkerData(ref reader, ref writer);
if (!JpegScanHeader.TryParse(buffer, false, out JpegScanHeader scanHeader, out _))
{
ThrowInvalidDataException(reader.ConsumedByteCount - (int)buffer.Length, "Failed to parse scan header.");
}
CopyScanBaseline(ref reader, ref writer, scanHeader);
break;
case JpegMarker.DefineRestart0:
case JpegMarker.DefineRestart1:
case JpegMarker.DefineRestart2:
case JpegMarker.DefineRestart3:
case JpegMarker.DefineRestart4:
case JpegMarker.DefineRestart5:
case JpegMarker.DefineRestart6:
case JpegMarker.DefineRestart7:
writer.WriteMarker(marker);
break;
case JpegMarker.EndOfImage:
writer.WriteMarker(JpegMarker.EndOfImage);
eoiReached = true;
break;
default:
if (strip)
{
SkipMarkerData(ref reader);
}
else
{
writer.WriteMarker(marker);
CopyMarkerData(ref reader, ref writer);
}
break;
}
}
writer.Flush();
}
internal bool ShadowEquals(JpegScanHeader other)
{
return(NumberOfComponents == other.NumberOfComponents && StartOfSpectralSelection == other.StartOfSpectralSelection && EndOfSpectralSelection == other.EndOfSpectralSelection &&
SuccessiveApproximationBitPositionHigh == other.SuccessiveApproximationBitPositionHigh && SuccessiveApproximationBitPositionLow == other.SuccessiveApproximationBitPositionLow);
}
