Example #1
0
        /// <para>Changes the current bitmap with a custom opacity level.  Here is where all happens!</para>
        public void SetBitmap(Bitmap bm, byte opacity)
        {
            if (bm.PixelFormat != PixelFormat.Format32bppArgb)
            {
                throw new ApplicationException("The bitmap must be 32ppp with alpha-channel.");
            }

            // The idea of this is very simple,
            // 1. Create a compatible DC with screen;
            // 2. Select the bitmap with 32bpp with alpha-channel in the compatible DC;
            // 3. Call the UpdateLayeredWindow.

            var screenDc  = Win32.GetDC(IntPtr.Zero);
            var memDc     = Win32.CreateCompatibleDC(screenDc);
            var hBitmap   = IntPtr.Zero;
            var oldBitmap = IntPtr.Zero;

            try
            {
                hBitmap   = bm.GetHbitmap(Color.FromArgb(0)); // grab a GDI handle from this GDI+ bitmap
                oldBitmap = Win32.SelectObject(memDc, hBitmap);

                var size        = new Win32.Size(bm.Width, bm.Height);
                var pointSource = new Win32.Point(0, 0);
                var topPos      = new Win32.Point(Left, Top);
                var blend       = new Win32.BLENDFUNCTION
                {
                    BlendOp             = Win32.AC_SRC_OVER,
                    BlendFlags          = 0,
                    SourceConstantAlpha = opacity,
                    AlphaFormat         = Win32.AC_SRC_ALPHA
                };

                Win32.UpdateLayeredWindow(Handle, screenDc, ref topPos, ref size, memDc, ref pointSource, 0, ref blend, Win32.ULW_ALPHA);
            }
            finally
            {
                Win32.ReleaseDC(IntPtr.Zero, screenDc);
                if (hBitmap != IntPtr.Zero)
                {
                    Win32.SelectObject(memDc, oldBitmap);
                    //Windows.DeleteObject(hBitmap); // The documentation says that we have to use the Windows.DeleteObject... but since there is no such method I use the normal DeleteObject from Win32 GDI and it's working fine without any resource leak.
                    Win32.DeleteObject(hBitmap);
                }
                Win32.DeleteDC(memDc);
            }
        }
        /// <para>Changes the current bitmap with a custom opacity level.  Here is where all happens!</para>
        public void SetBitmap(Bitmap bitmap, byte opacity)
        {
            if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
                throw new ApplicationException("The bitmap must be 32ppp with alpha-channel.");

            // The idea of this is very simple,
            // 1. Create a compatible DC with screen;
            // 2. Select the bitmap with 32bpp with alpha-channel in the compatible DC;
            // 3. Call the UpdateLayeredWindow.

            IntPtr screenDc = Win32.GetDC(IntPtr.Zero);
            IntPtr memDc = Win32.CreateCompatibleDC(screenDc);
            IntPtr hBitmap = IntPtr.Zero;
            IntPtr oldBitmap = IntPtr.Zero;

            try
            {
                hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));  // grab a GDI handle from this GDI+ bitmap
                oldBitmap = Win32.SelectObject(memDc, hBitmap);

                Win32.Size size = new Win32.Size(bitmap.Width, bitmap.Height);
                Win32.Point pointSource = new Win32.Point(0, 0);
                Win32.Point topPos = new Win32.Point(Left, Top);
                Win32.BLENDFUNCTION blend = new Win32.BLENDFUNCTION();
                blend.BlendOp = Win32.AC_SRC_OVER;
                blend.BlendFlags = 0;
                blend.SourceConstantAlpha = opacity;
                blend.AlphaFormat = Win32.AC_SRC_ALPHA;

                Win32.UpdateLayeredWindow(Handle, screenDc, ref topPos, ref size, memDc, ref pointSource, 0, ref blend, Win32.ULW_ALPHA);
            }
            finally
            {
                Win32.ReleaseDC(IntPtr.Zero, screenDc);
                if (hBitmap != IntPtr.Zero)
                {
                    Win32.SelectObject(memDc, oldBitmap);
                    //Windows.DeleteObject(hBitmap); // The documentation says that we have to use the Windows.DeleteObject... but since there is no such method I use the normal DeleteObject from Win32 GDI and it's working fine without any resource leak.
                    Win32.DeleteObject(hBitmap);
                }
                Win32.DeleteDC(memDc);
            }
        }