public void SetBitmap(Bitmap bitmap, byte opacity)
{
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
throw new FormatException("Format32bppArgb bitmap required");
IntPtr screenDc = NativeMethods.GetDC(IntPtr.Zero);
IntPtr memDc = NativeMethods.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr oldBitmap = IntPtr.Zero;
try
{
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
oldBitmap = NativeMethods.SelectObject(memDc, hBitmap);
NativeStructs.SIZE size = new NativeStructs.SIZE(bitmap.Width, bitmap.Height);
NativeStructs.POINT pointSource = new NativeStructs.POINT(0, 0);
NativeStructs.POINT topPos = new NativeStructs.POINT(Left, Top);
NativeStructs.BLENDFUNCTION blend = new NativeStructs.BLENDFUNCTION();
blend.BlendOp = NativeConsts.AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = opacity;
blend.AlphaFormat = NativeConsts.AC_SRC_ALPHA;
NativeMethods.UpdateLayeredWindow(Handle, screenDc, ref topPos, ref size, memDc, ref pointSource, 0, ref blend, NativeConsts.ULW_ALPHA);
}
finally
{
NativeMethods.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
NativeMethods.SelectObject(memDc, oldBitmap);
NativeMethods.DeleteObject(hBitmap);
}
NativeMethods.DeleteDC(memDc);
}
}
public static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref NativeStructs.POINT pptDst, ref NativeStructs.SIZE psize, IntPtr hdcSrc, ref NativeStructs.POINT pprSrc, Int32 crKey, ref NativeStructs.BLENDFUNCTION pblend, Int32 dwFlags);
