public void BlitAdditive(JBitmap target, int px, int py, float strength)
{
//currently only supported for 8 bpp source / target
if (bitmapData.PixelFormat == System.Drawing.Imaging.PixelFormat.Format8bppIndexed &&
target.bitmapData.PixelFormat == System.Drawing.Imaging.PixelFormat.Format8bppIndexed)
{
int targetStartX, targetEndX;
int targetStartY, targetEndY;
int copyW, copyH;
targetStartX = Math.Max(px, 0);
targetEndX = Math.Min(px + bitmapData.Width, target.bitmapData.Width);
targetStartY = Math.Max(py, 0);
targetEndY = Math.Min(py + bitmapData.Height, target.bitmapData.Height);
copyW = targetEndX - targetStartX;
copyH = targetEndY - targetStartY;
if (copyW < 0)
{
return;
}
if (copyH < 0)
{
return;
}
int sourceStartX = targetStartX - px;
int sourceStartY = targetStartY - py;
unsafe
{
byte* sourcePtr = (byte*)(bitmapData.Scan0);
byte* targetPtr = (byte*)(target.bitmapData.Scan0);
int sum;
byte* targetY = targetPtr + targetStartY * target.bitmapData.Stride;
byte* sourceY = sourcePtr + sourceStartY * bitmapData.Stride;
for (int y = 0; y < copyH; y++, targetY += target.bitmapData.Stride, sourceY += bitmapData.Stride)
{
byte* targetOffset = targetY + targetStartX;
byte* sourceOffset = sourceY + sourceStartX;
for (int x = 0; x < copyW; x++, targetOffset++, sourceOffset++)
{
sum = (int)*(targetOffset) + (int) (*(sourceOffset) * strength);
if (sum > 255)
{
*(targetOffset) = 255;
} else {
*(targetOffset) = (byte)sum;
}
}
}
}
}
}
