/// <summary>
/// Try to convert from YCbCr to RGB colors
/// </summary>
/// <param name="sourceColorspace">The colorspace of the luma and chroma</param>
/// <param name="luma">The luma plane</param>
/// <param name="blueDifferential">The blue differential (Cb) plane</param>
/// <param name="redDifferential">The red differential (Cr) plane</param>
/// <param name="width">The width of the frame</param>
/// <param name="height">The height of the frame</param>
/// <returns>An RGB plane if this function succeeds. None otherwise</returns>
/// <remarks>
/// FFMPEG outputs 420mpeg2 (where the chroma samples are aligned horizontally, but
/// shifted a half-pixel down).
/// https://msdn.microsoft.com/en-us/library/windows/desktop/dd206750(v=vs.85).aspx
/// </remarks>
public static Maybe<Color[][]> TryConvertFrameToRGB(
ColorSpace sourceColorspace,
byte[][] luma,
byte[][] blueDifferential,
byte[][] redDifferential,
int width,
int height
)
{
var inFrames = new YCrCbFrame
{
ColorSpace = sourceColorspace,
Luma = luma,
Cb = blueDifferential,
Cr = redDifferential,
Width = width,
Height = height,
};
if (Equals(sourceColorspace, ColorSpace.FourFourFour))
{
return TryConvertYCbCr444ToRGB(inFrames);
}
if (Equals(sourceColorspace, ColorSpace.FourTwoTwo))
{
return from horizontalUpconvert in TryConvert422To444(inFrames)
select TryConvertYCbCr444ToRGB(horizontalUpconvert);
}
if (Equals(sourceColorspace, ColorSpace.FourTwoZeroMpeg2))
{
return from verticalUpconvert in TryConvert420To422(inFrames)
from horizontalUpconvert in TryConvert422To444(verticalUpconvert)
select TryConvertYCbCr444ToRGB(horizontalUpconvert);
}
return Maybe<Color[][]>.Nothing;
}
private static Maybe<YCrCbFrame> TryConvert422To444(
YCrCbFrame subsampledFrames
)
{
var outFrames = new YCrCbFrame
{
ColorSpace = ColorSpace.FourTwoTwo,
Luma = subsampledFrames.Luma,
Cb = new byte[subsampledFrames.Height][],
Cr = new byte[subsampledFrames.Height][],
Width = subsampledFrames.Width,
Height = subsampledFrames.Height,
};
UpsampleHorizontalResolution(subsampledFrames.Cb, outFrames.Cb);
UpsampleHorizontalResolution(subsampledFrames.Cr, outFrames.Cr);
return outFrames.ToMaybe();
}
private static Maybe<Color[][]> TryConvertYCbCr444ToRGB(
YCrCbFrame inFrame
)
{
try
{
Color[][] frame = new Color[inFrame.Height][];
for (int row = 0; row < inFrame.Height; row++)
{
frame[row] = new Color[inFrame.Width];
for (int col = 0; col < inFrame.Width; col++)
{
byte currentLuma = inFrame.Luma[row][col];
byte currentCb = inFrame.Cb[row][col];
byte currentCr = inFrame.Cr[row][col];
frame[row][col] = ConvertYUVToRGB(currentLuma, currentCb, currentCr);
}
}
if (frame.Length != inFrame.Height || frame[0].Length != inFrame.Width)
{
return Maybe<Color[][]>.Nothing;
}
return frame.ToMaybe();
}
catch (Exception)
{
}
return Maybe<Color[][]>.Nothing;
}
/// <summary>
/// Vertically upconvert from 4:2:0 to 4:2:2
/// </summary>
/// <param name="subsampledFrames"></param>
/// <returns></returns>
private static Maybe<YCrCbFrame> TryConvert420To422(
YCrCbFrame subsampledFrames
)
{
var outFrames = new YCrCbFrame
{
ColorSpace = ColorSpace.FourTwoTwo,
Luma = subsampledFrames.Luma,
Cb = new byte[subsampledFrames.Height][],
Cr = new byte[subsampledFrames.Height][],
Width = subsampledFrames.Width,
Height = subsampledFrames.Height,
};
// Initialize all chroma planes
int widthOfChromaRow = subsampledFrames.Cb[0].Length;
for (int row = 0; row < outFrames.Height; row++)
{
outFrames.Cb[row] = new byte[widthOfChromaRow];
outFrames.Cr[row] = new byte[widthOfChromaRow];
}
UpsampleVerticalResolution(subsampledFrames.Cb, outFrames.Cb);
UpsampleVerticalResolution(subsampledFrames.Cr, outFrames.Cr);
return outFrames.ToMaybe();
}
