public void SelectBitmap(Bitmap bitmap, int opacity)
{
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new ApplicationException("The bitmap must be 32bpp with alpha-channel.");
}
IntPtr screenDc = NativeMethods.GetDC(IntPtr.Zero);
IntPtr memDc = NativeMethods.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr hOldBitmap = IntPtr.Zero;
try
{
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
hOldBitmap = NativeMethods.SelectObject(memDc, hBitmap);
SIZE newSize = new SIZE(bitmap.Width, bitmap.Height);
POINT sourceLocation = new POINT(0, 0);
POINT newLocation = new POINT(this.Left, this.Top);
BLENDFUNCTION blend = new BLENDFUNCTION();
blend.BlendOp = NativeMethods.AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = (byte)opacity;
blend.AlphaFormat = NativeMethods.AC_SRC_ALPHA;
NativeMethods.UpdateLayeredWindow(this.Handle, screenDc, ref newLocation, ref newSize, memDc, ref sourceLocation, 0, ref blend, NativeMethods.ULW_ALPHA);
}
finally
{
NativeMethods.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
NativeMethods.SelectObject(memDc, hOldBitmap);
NativeMethods.DeleteObject(hBitmap);
}
NativeMethods.DeleteDC(memDc);
}
}
public static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref POINT pptDst, ref SIZE psize, IntPtr hdcSrc, ref POINT pptSrc, uint crKey, [In] ref BLENDFUNCTION pblend, uint dwFlags);