public JpegHuffmanProgressiveScanDecoder(JpegDecoder decoder, JpegFrameHeader frameHeader) : base(decoder)
{
_frameHeader = frameHeader;
// Compute maximum sampling factor
int maxHorizontalSampling = 1;
int maxVerticalSampling = 1;
foreach (JpegFrameComponentSpecificationParameters currentFrameComponent in frameHeader.Components !)
{
maxHorizontalSampling = Math.Max(maxHorizontalSampling, currentFrameComponent.HorizontalSamplingFactor);
maxVerticalSampling = Math.Max(maxVerticalSampling, currentFrameComponent.VerticalSamplingFactor);
}
_mcusPerLine = (frameHeader.SamplesPerLine + 8 * maxHorizontalSampling - 1) / (8 * maxHorizontalSampling);
_mcusPerColumn = (frameHeader.NumberOfLines + 8 * maxVerticalSampling - 1) / (8 * maxVerticalSampling);
_levelShift = 1 << (frameHeader.SamplePrecision - 1);
JpegBlockOutputWriter?outputWriter = decoder.GetOutputWriter();
if (outputWriter is null)
{
ThrowInvalidDataException("Output writer is not set.");
}
_outputWriter = outputWriter;
_allocator = new JpegBlockAllocator(decoder.MemoryPool);
_allocator.Allocate(frameHeader);
// Pre-allocate the JpegDecodeComponent instances
_components = new JpegHuffmanDecodingComponent[frameHeader.NumberOfComponents];
for (int i = 0; i < _components.Length; i++)
{
_components[i] = new JpegHuffmanDecodingComponent();
}
}
private void DecodeProgressiveDataInterleaved(ref JpegReader reader, JpegScanHeader scanHeader, Span <JpegArithmeticDecodingComponent> components)
{
foreach (JpegArithmeticDecodingComponent component in components)
{
if (component.DcTable is null || component.DcStatistics is null)
{
ThrowInvalidDataException();
}
}
JpegBlockAllocator allocator = _allocator;
JpegBitReader bitReader = new JpegBitReader(reader.RemainingBytes);
int mcusPerColumn = _mcusPerColumn;
int mcusPerLine = _mcusPerLine;
for (int rowMcu = 0; rowMcu < mcusPerColumn; rowMcu++)
{
for (int colMcu = 0; colMcu < mcusPerLine; colMcu++)
{
foreach (JpegArithmeticDecodingComponent component in components)
{
int index = component.ComponentIndex;
int h = component.HorizontalSamplingFactor;
int v = component.VerticalSamplingFactor;
int offsetX = colMcu * h;
int offsetY = rowMcu * v;
for (int y = 0; y < v; y++)
{
int blockOffsetY = offsetY + y;
for (int x = 0; x < h; x++)
{
ref JpegBlock8x8 blockRef = ref allocator.GetBlockReference(index, offsetX + x, blockOffsetY);
ReadBlockProgressiveDC(ref bitReader, component, scanHeader, ref blockRef);
}
}
}
if (!HandleRestart(ref bitReader, ref reader, ref scanHeader, ref MemoryMarshal.GetReference(components), components.Length))
{
return;
}
}
}
private void DecodeProgressiveDataInterleaved(ref JpegReader reader, JpegScanHeader scanHeader, Span <JpegHuffmanDecodingComponent> components)
{
JpegBlockAllocator allocator = _allocator;
JpegBitReader bitReader = new JpegBitReader(reader.RemainingBytes);
int mcusPerColumn = _mcusPerColumn;
int mcusPerLine = _mcusPerLine;
for (int rowMcu = 0; rowMcu < mcusPerColumn; rowMcu++)
{
for (int colMcu = 0; colMcu < mcusPerLine; colMcu++)
{
foreach (JpegHuffmanDecodingComponent component in components)
{
int index = component.ComponentIndex;
int h = component.HorizontalSamplingFactor;
int v = component.VerticalSamplingFactor;
int offsetX = colMcu * h;
int offsetY = rowMcu * v;
for (int y = 0; y < v; y++)
{
int blockOffsetY = offsetY + y;
for (int x = 0; x < h; x++)
{
ref JpegBlock8x8 blockRef = ref allocator.GetBlockReference(index, offsetX + x, blockOffsetY);
ReadBlockProgressiveDC(ref bitReader, component, scanHeader, ref blockRef);
}
}
}
if (!HandleRestart(ref bitReader, ref reader))
{
return;
}
}
}
