private void WithTransparentCanvas(Rectangle rect, byte alpha, bool copySource, Action <Win32Canvas> action)
{
if (rect.Width <= 0 || rect.Height <= 0 || alpha == 0)
{
return;
}
IntPtr memoryHdc = Gdi32API.CreateCompatibleDCChecked(hdc);
try
{
IntPtr memoryBitmap = Gdi32API.CreateCompatibleBitmapChecked(hdc, rect.Width, rect.Height);
try
{
var originalBitmap = Gdi32API.SelectObjectChecked(memoryHdc, memoryBitmap);
try
{
if (copySource)
{
Gdi32API.BitBlt(memoryHdc, 0, 0, rect.Width, rect.Height, hdc, rect.X, rect.Y, GDI32RasterOperation.SRCCOPY);
}
using (Win32Canvas memoryCanvas = new Win32Canvas(memoryHdc, offset, objectCache))
{
action(memoryCanvas);
}
Gdi32API.GdiAlphaBlend
(
hdc,
rect.X, rect.Y, rect.Width, rect.Height,
memoryHdc,
0, 0, rect.Width, rect.Height,
BLENDFUNCTION.ConstantAlpha(alpha)
);
}
finally
{
Gdi32API.SelectObjectChecked(memoryHdc, originalBitmap);
}
}
finally
{
Gdi32API.DeleteObject(memoryBitmap);
}
}
finally
{
Gdi32API.DeleteDC(memoryHdc);
}
}
public void CopyTo(IntPtr hdc, int x, int y)
{
Gdi32API.BitBlt(hdc, x, y, width, height, bitmapHdc, 0, 0, GDI32RasterOperation.SRCCOPY);
}
