/// <summary>
/// Encodes the image with subsampling. The Cb and Cr components are each subsampled
/// at a factor of 2 both horizontally and vertically.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="pixels">The pixel accessor providing access to the image pixels.</param>
private void Encode420 <TPixel>(Image <TPixel> pixels)
where TPixel : struct, IPixel <TPixel>
{
// TODO: Need a JpegScanEncoder<TPixel> class or struct that encapsulates the scan-encoding implementation. (Similar to JpegScanDecoder.)
Block8x8F b = default;
BlockQuad cb = default;
BlockQuad cr = default;
var cbPtr = (Block8x8F *)cb.Data;
var crPtr = (Block8x8F *)cr.Data;
Block8x8F temp1 = default;
Block8x8F temp2 = default;
Block8x8F onStackLuminanceQuantTable = this.luminanceQuantTable;
Block8x8F onStackChrominanceQuantTable = this.chrominanceQuantTable;
var unzig = ZigZag.CreateUnzigTable();
var pixelConverter = YCbCrForwardConverter <TPixel> .Create();
// ReSharper disable once InconsistentNaming
int prevDCY = 0, prevDCCb = 0, prevDCCr = 0;
for (int y = 0; y < pixels.Height; y += 16)
{
for (int x = 0; x < pixels.Width; x += 16)
{
for (int i = 0; i < 4; i++)
{
int xOff = (i & 1) * 8;
int yOff = (i & 2) * 4;
pixelConverter.Convert(pixels.Frames.RootFrame, x + xOff, y + yOff);
cbPtr[i] = pixelConverter.Cb;
crPtr[i] = pixelConverter.Cr;
prevDCY = this.WriteBlock(
QuantIndex.Luminance,
prevDCY,
&pixelConverter.Y,
&temp1,
&temp2,
&onStackLuminanceQuantTable,
unzig.Data);
}
Block8x8F.Scale16X16To8X8(&b, cbPtr);
prevDCCb = this.WriteBlock(
QuantIndex.Chrominance,
prevDCCb,
&b,
&temp1,
&temp2,
&onStackChrominanceQuantTable,
unzig.Data);
Block8x8F.Scale16X16To8X8(&b, crPtr);
prevDCCr = this.WriteBlock(
QuantIndex.Chrominance,
prevDCCr,
&b,
&temp1,
&temp2,
&onStackChrominanceQuantTable,
unzig.Data);
}
}
}
/// <summary>
/// Encodes the image with subsampling. The Cb and Cr components are each subsampled
/// at a factor of 2 both horizontally and vertically.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <param name="pixels">The pixel accessor providing access to the image pixels.</param>
private void Encode420 <TColor>(PixelAccessor <TColor> pixels)
where TColor : struct, IPackedPixel, IEquatable <TColor>
{
// TODO: Need a JpegScanEncoder<TColor> class or struct that encapsulates the scan-encoding implementation. (Similar to JpegScanDecoder.)
Block8x8F b = default(Block8x8F);
BlockQuad cb = default(BlockQuad);
BlockQuad cr = default(BlockQuad);
Block8x8F *cbPtr = (Block8x8F *)cb.Data;
Block8x8F *crPtr = (Block8x8F *)cr.Data;
Block8x8F temp1 = default(Block8x8F);
Block8x8F temp2 = default(Block8x8F);
Block8x8F onStackLuminanceQuantTable = this.luminanceQuantTable;
Block8x8F onStackChrominanceQuantTable = this.chrominanceQuantTable;
UnzigData unzig = UnzigData.Create();
// ReSharper disable once InconsistentNaming
int prevDCY = 0, prevDCCb = 0, prevDCCr = 0;
using (PixelArea <TColor> rgbBytes = new PixelArea <TColor>(8, 8, ComponentOrder.Xyz))
{
for (int y = 0; y < pixels.Height; y += 16)
{
for (int x = 0; x < pixels.Width; x += 16)
{
for (int i = 0; i < 4; i++)
{
int xOff = (i & 1) * 8;
int yOff = (i & 2) * 4;
ToYCbCr(pixels, x + xOff, y + yOff, &b, cbPtr + i, crPtr + i, rgbBytes);
prevDCY = this.WriteBlock(
QuantIndex.Luminance,
prevDCY,
&b,
&temp1,
&temp2,
&onStackLuminanceQuantTable,
unzig.Data);
}
Block8x8F.Scale16X16To8X8(&b, cbPtr);
prevDCCb = this.WriteBlock(
QuantIndex.Chrominance,
prevDCCb,
&b,
&temp1,
&temp2,
&onStackChrominanceQuantTable,
unzig.Data);
Block8x8F.Scale16X16To8X8(&b, crPtr);
prevDCCr = this.WriteBlock(
QuantIndex.Chrominance,
prevDCCr,
&b,
&temp1,
&temp2,
&onStackChrominanceQuantTable,
unzig.Data);
}
}
}
}
