private void PerformDrawWithDithering(IQuantizingSession quantizingSession, IDitheringSession ditheringSession)
{
IBitmapDataInternal source = Source;
IBitmapDataInternal target = Target;
Point sourceLocation = SourceRectangle.Location;
Point targetLocation = TargetRectangle.Location;
int sourceWidth = SourceRectangle.Width;
// Sequential processing
if (ditheringSession.IsSequential || SourceRectangle.Width < parallelThreshold >> ditheringScale)
{
context.Progress?.New(DrawingOperation.ProcessingPixels, SourceRectangle.Height);
for (int y = 0; y < SourceRectangle.Height; y++)
{
if (context.IsCancellationRequested)
{
return;
}
ProcessRow(y);
context.Progress?.Increment();
}
return;
}
// Parallel processing
ParallelHelper.For(context, DrawingOperation.ProcessingPixels, 0, SourceRectangle.Height, ProcessRow);
#region Local Methods
void ProcessRow(int y)
{
IDitheringSession session = ditheringSession;
IBitmapDataRowInternal rowSrc = source.DoGetRow(sourceLocation.Y + y);
IBitmapDataRowInternal rowDst = target.DoGetRow(targetLocation.Y + y);
int offsetSrc = sourceLocation.X;
int offsetDst = targetLocation.X;
byte alphaThreshold = quantizingSession.AlphaThreshold;
int width = sourceWidth;
for (int x = 0; x < width; x++)
{
Color32 colorSrc = rowSrc.DoGetColor32(x + offsetSrc);
// fully solid source: overwrite
if (colorSrc.A == Byte.MaxValue)
{
rowDst.DoSetColor32(x + offsetDst, session.GetDitheredColor(colorSrc, x, y));
continue;
}
// fully transparent source: skip
if (colorSrc.A == 0)
{
continue;
}
// source here has a partial transparency: we need to read the target color
int pos = x + offsetDst;
Color32 colorDst = rowDst.DoGetColor32(pos);
// non-transparent target: blending
if (colorDst.A != 0)
{
colorSrc = colorDst.A == Byte.MaxValue
// target pixel is fully solid: simple blending
? colorSrc.BlendWithBackground(colorDst)
// both source and target pixels are partially transparent: complex blending
: colorSrc.BlendWith(colorDst);
}
// overwriting target color only if blended color has high enough alpha
if (colorSrc.A < alphaThreshold)
{
continue;
}
rowDst.DoSetColor32(pos, session.GetDitheredColor(colorSrc, x, y));
}
}
#endregion
}
internal void PerformDrawDirect()
{
IBitmapDataInternal source = Source;
IBitmapDataInternal target = Target;
Point sourceLocation = SourceRectangle.Location;
Point targetLocation = TargetRectangle.Location;
int sourceWidth = SourceRectangle.Width;
// Sequential processing
if (SourceRectangle.Width < parallelThreshold)
{
if (Target.IsFastPremultiplied())
{
context.Progress?.New(DrawingOperation.ProcessingPixels, SourceRectangle.Height);
for (int y = 0; y < SourceRectangle.Height; y++)
{
if (context.IsCancellationRequested)
{
return;
}
ProcessRowPremultiplied(y);
context.Progress?.Increment();
}
}
else
{
context.Progress?.New(DrawingOperation.ProcessingPixels, SourceRectangle.Height);
for (int y = 0; y < SourceRectangle.Height; y++)
{
if (context.IsCancellationRequested)
{
return;
}
ProcessRowStraight(y);
context.Progress?.Increment();
}
}
return;
}
// Parallel processing
Action <int> processRow = Target.IsFastPremultiplied()
? ProcessRowPremultiplied
: (Action <int>)ProcessRowStraight;
ParallelHelper.For(context, DrawingOperation.ProcessingPixels, 0, SourceRectangle.Height, processRow);
#region Local Methods
void ProcessRowStraight(int y)
{
IBitmapDataRowInternal rowSrc = source.DoGetRow(sourceLocation.Y + y);
IBitmapDataRowInternal rowDst = target.DoGetRow(targetLocation.Y + y);
int offsetSrc = sourceLocation.X;
int offsetDst = targetLocation.X;
byte alphaThreshold = target.AlphaThreshold;
int width = sourceWidth;
for (int x = 0; x < width; x++)
{
Color32 colorSrc = rowSrc.DoGetColor32(x + offsetSrc);
// fully solid source: overwrite
if (colorSrc.A == Byte.MaxValue)
{
rowDst.DoSetColor32(x + offsetDst, colorSrc);
continue;
}
// fully transparent source: skip
if (colorSrc.A == 0)
{
continue;
}
// source here has a partial transparency: we need to read the target color
int pos = x + offsetDst;
Color32 colorDst = rowDst.DoGetColor32(pos);
// non-transparent target: blending
if (colorDst.A != 0)
{
colorSrc = colorDst.A == Byte.MaxValue
// target pixel is fully solid: simple blending
? colorSrc.BlendWithBackground(colorDst)
// both source and target pixels are partially transparent: complex blending
: colorSrc.BlendWith(colorDst);
}
// overwriting target color only if blended color has high enough alpha
if (colorSrc.A < alphaThreshold)
{
continue;
}
rowDst.DoSetColor32(pos, colorSrc);
}
}
void ProcessRowPremultiplied(int y)
{
IBitmapDataRowInternal rowSrc = source.DoGetRow(sourceLocation.Y + y);
IBitmapDataRowInternal rowDst = target.DoGetRow(targetLocation.Y + y);
int offsetSrc = sourceLocation.X;
int offsetDst = targetLocation.X;
int width = sourceWidth;
for (int x = 0; x < width; x++)
{
Color32 colorSrc = rowSrc.DoGetColor32Premultiplied(x + offsetSrc);
// fully solid source: overwrite
if (colorSrc.A == Byte.MaxValue)
{
rowDst.DoSetColor32Premultiplied(x + offsetDst, colorSrc);
continue;
}
// fully transparent source: skip
if (colorSrc.A == 0)
{
continue;
}
// source here has a partial transparency: we need to read the target color
int pos = x + offsetDst;
Color32 colorDst = rowDst.DoGetColor32Premultiplied(pos);
// non-transparent target: blending
if (colorDst.A != 0)
{
colorSrc = colorSrc.BlendWithPremultiplied(colorDst);
}
rowDst.DoSetColor32Premultiplied(pos, colorSrc);
}
}
#endregion
}