public YCbCrForwardConverter420(ImageFrame <TPixel> frame)
{
// matrices would be filled during convert calls
this.YLeft = default;
this.YRight = default;
this.Cb = default;
this.Cr = default;
// temporal pixel buffers
this.pixelSpan = new TPixel[PixelsPerSample].AsSpan();
this.rgbSpan = MemoryMarshal.Cast <byte, Rgb24>(new byte[RgbSpanByteSize + RgbToYCbCrConverterVectorized.AvxCompatibilityPadding].AsSpan());
// frame data
this.samplingAreaSize = new Size(frame.Width, frame.Height);
this.config = frame.GetConfiguration();
// conversion vector fallback data
if (!RgbToYCbCrConverterVectorized.IsSupported)
{
this.colorTables = RgbToYCbCrConverterLut.Create();
}
else
{
this.colorTables = default;
}
}
/// <summary>
/// Initializes the YCbCr tables
/// </summary>
/// <returns>The initialized <see cref="RgbToYCbCrConverterLut"/></returns>
public static RgbToYCbCrConverterLut Create()
{
RgbToYCbCrConverterLut tables = default;
for (int i = 0; i <= 255; i++)
{
// The values for the calculations are left scaled up since we must add them together before rounding.
tables.YRTable[i] = Fix(0.299F) * i;
tables.YGTable[i] = Fix(0.587F) * i;
tables.YBTable[i] = (Fix(0.114F) * i) + Half;
tables.CbRTable[i] = (-Fix(0.168735892F)) * i;
tables.CbGTable[i] = (-Fix(0.331264108F)) * i;
// We use a rounding fudge - factor of 0.5 - epsilon for Cb and Cr.
// This ensures that the maximum output will round to 255
// not 256, and thus that we don't have to range-limit.
//
// B=>Cb and R=>Cr tables are the same
tables.CbBTable[i] = (Fix(0.5F) * i) + CBCrOffset + Half - 1;
tables.CrGTable[i] = (-Fix(0.418687589F)) * i;
tables.CrBTable[i] = (-Fix(0.081312411F)) * i;
}
return(tables);
}
public static YCbCrForwardConverter <TPixel> Create()
{
var result = default(YCbCrForwardConverter <TPixel>);
if (!RgbToYCbCrConverterVectorized.IsSupported)
{
// Avoid creating lookup tables, when vectorized converter is supported
result.colorTables = RgbToYCbCrConverterLut.Create();
}
return(result);
}
