public static void ReleaseHBitmap(IntPtr hBitmap)
{
if (hBitmap != IntPtr.Zero)
{
GdiplusPInvoke.DeleteObject(hBitmap);
}
}
public static void SetBitmap(Bitmap bitmap, byte opacity, IntPtr handle, int left, int top, int width, int height)
{
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new ApplicationException("The bitmap must be 32ppp with alpha-channel.");
}
var screenDc = GdiplusPInvoke.GetDC(IntPtr.Zero);
var memDc = GdiplusPInvoke.CreateCompatibleDC(screenDc);
var oldBitmap = IntPtr.Zero;
var hBitmap = IntPtr.Zero;
try
{
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
oldBitmap = GdiplusPInvoke.SelectObject(memDc, hBitmap);
var size = new Size(width, height);
var pointSource = new Point(0, 0);
var topPos = new Point(left, top);
var blend = new BLENDFUNCTION
{
BlendOp = GdiplusPInvoke.AC_SRC_OVER,
BlendFlags = 0,
SourceConstantAlpha = opacity,
AlphaFormat = GdiplusPInvoke.AC_SRC_ALPHA
};
GdiplusPInvoke.UpdateLayeredWindow(
handle,
screenDc,
ref topPos,
ref size,
memDc,
ref pointSource,
0,
ref blend,
GdiplusPInvoke.ULW_ALPHA);
}
finally
{
GdiplusPInvoke.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
GdiplusPInvoke.DeleteObject(hBitmap);
GdiplusPInvoke.SelectObject(memDc, oldBitmap);
}
GdiplusPInvoke.DeleteDC(memDc);
}
}
