private static void ReverseChromaSubSampling(int width, int height, int horizontalSubSampling, int verticalSubSampling, ReadOnlySpan <byte> source, Span <byte> destination)
{
// If width and height are not multiples of ChromaSubsampleHoriz and ChromaSubsampleVert respectively,
// then the source data will be padded.
width += TiffUtils.PaddingToNextInteger(width, horizontalSubSampling);
height += TiffUtils.PaddingToNextInteger(height, verticalSubSampling);
int blockWidth = width / horizontalSubSampling;
int blockHeight = height / verticalSubSampling;
int cbCrOffsetInBlock = horizontalSubSampling * verticalSubSampling;
int blockByteCount = cbCrOffsetInBlock + 2;
for (int blockRow = blockHeight - 1; blockRow >= 0; blockRow--)
{
for (int blockCol = blockWidth - 1; blockCol >= 0; blockCol--)
{
int blockOffset = (blockRow * blockWidth) + blockCol;
ReadOnlySpan <byte> blockData = source.Slice(blockOffset * blockByteCount, blockByteCount);
byte cr = blockData[cbCrOffsetInBlock + 1];
byte cb = blockData[cbCrOffsetInBlock];
for (int row = verticalSubSampling - 1; row >= 0; row--)
{
for (int col = horizontalSubSampling - 1; col >= 0; col--)
{
int offset = 3 * ((((blockRow * verticalSubSampling) + row) * width) + (blockCol * horizontalSubSampling) + col);
destination[offset + 2] = cr;
destination[offset + 1] = cb;
destination[offset] = blockData[(row * horizontalSubSampling) + col];
}
}
}
}
}
/// <inheritdoc/>
public override void Decode(IMemoryOwner <byte>[] data, Buffer2D <TPixel> pixels, int left, int top, int width, int height)
{
Span <byte> yData = data[0].GetSpan();
Span <byte> cbData = data[1].GetSpan();
Span <byte> crData = data[2].GetSpan();
if (this.ycbcrSubSampling != null && !(this.ycbcrSubSampling[0] == 1 && this.ycbcrSubSampling[1] == 1))
{
ReverseChromaSubSampling(width, height, this.ycbcrSubSampling[0], this.ycbcrSubSampling[1], cbData, crData);
}
var color = default(TPixel);
int offset = 0;
int widthPadding = 0;
if (this.ycbcrSubSampling != null)
{
// Round to the next integer multiple of horizontalSubSampling.
widthPadding = TiffUtils.PaddingToNextInteger(width, this.ycbcrSubSampling[0]);
}
for (int y = top; y < top + height; y++)
{
Span <TPixel> pixelRow = pixels.DangerousGetRowSpan(y).Slice(left, width);
for (int x = 0; x < pixelRow.Length; x++)
{
Rgba32 rgba = this.converter.ConvertToRgba32(yData[offset], cbData[offset], crData[offset]);
color.FromRgba32(rgba);
pixelRow[x] = color;
offset++;
}
offset += widthPadding;
}
}
private static void ReverseChromaSubSampling(int width, int height, int horizontalSubSampling, int verticalSubSampling, Span <byte> planarCb, Span <byte> planarCr)
{
// If width and height are not multiples of ChromaSubsampleHoriz and ChromaSubsampleVert respectively,
// then the source data will be padded.
width += TiffUtils.PaddingToNextInteger(width, horizontalSubSampling);
height += TiffUtils.PaddingToNextInteger(height, verticalSubSampling);
for (int row = height - 1; row >= 0; row--)
{
for (int col = width - 1; col >= 0; col--)
{
int offset = (row * width) + col;
int subSampleOffset = (row / verticalSubSampling * (width / horizontalSubSampling)) + (col / horizontalSubSampling);
planarCb[offset] = planarCb[subSampleOffset];
planarCr[offset] = planarCr[subSampleOffset];
}
}
}
/// <inheritdoc/>
public override void Decode(ReadOnlySpan <byte> data, Buffer2D <TPixel> pixels, int left, int top, int width, int height)
{
ReadOnlySpan <byte> ycbcrData = data;
if (this.ycbcrSubSampling != null && !(this.ycbcrSubSampling[0] == 1 && this.ycbcrSubSampling[1] == 1))
{
// 4 extra rows and columns for possible padding.
int paddedWidth = width + 4;
int paddedHeight = height + 4;
int requiredBytes = paddedWidth * paddedHeight * 3;
using IMemoryOwner <byte> tmpBuffer = this.memoryAllocator.Allocate <byte>(requiredBytes);
Span <byte> tmpBufferSpan = tmpBuffer.GetSpan();
ReverseChromaSubSampling(width, height, this.ycbcrSubSampling[0], this.ycbcrSubSampling[1], data, tmpBufferSpan);
ycbcrData = tmpBufferSpan;
}
var color = default(TPixel);
int offset = 0;
int widthPadding = 0;
if (this.ycbcrSubSampling != null)
{
// Round to the next integer multiple of horizontalSubSampling.
widthPadding = TiffUtils.PaddingToNextInteger(width, this.ycbcrSubSampling[0]);
}
for (int y = top; y < top + height; y++)
{
Span <TPixel> pixelRow = pixels.GetRowSpan(y).Slice(left, width);
for (int x = 0; x < pixelRow.Length; x++)
{
Rgba32 rgba = this.converter.ConvertToRgba32(ycbcrData[offset], ycbcrData[offset + 1], ycbcrData[offset + 2]);
color.FromRgba32(rgba);
pixelRow[x] = color;
offset += 3;
}
offset += widthPadding * 3;
}
}