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);