anfuson - Professional Profile

public MainForm()
        {
            InitializeComponent();

            backBuffer = new Bitmap(this.ClientSize.Width, this.ClientSize.Height, System.Drawing.Imaging.PixelFormat.Format32bppRgb);

            // The other radio buttons have their tag set in InitializeComponent().
            radioButton4.Tag = Color.FromArgb(255, 255, 192);

            // Load the image to use with the AlphaBlend API.
            string path = System.IO.Path.GetDirectoryName(Assembly.GetExecutingAssembly().GetName().CodeBase); 
            constantAlphaImage = new Bitmap(path + @"\blendme.bmp");

            // Load the image with alpha data through Imaging.
            // We don't need the factory later, so it is local (and temporary).
            IImagingFactory factory = (IImagingFactory)Activator.CreateInstance(Type.GetTypeFromCLSID(new Guid("327ABDA8-072B-11D3-9D7B-0000F81EF32E")));
            factory.CreateImageFromFile(path + @"\ihavealpha.png", out imagingImage);

            // Load the image with alpha data from an embedded resource through Imaging
            // !! If your data source is not a MemoryStream, you will need to get your image data into a byte array and use it below. !!
            MemoryStream strm = (MemoryStream)Assembly.GetExecutingAssembly().GetManifestResourceStream("AlphaExample.embedded.png");
            byte[] pbBuf = strm.GetBuffer();
            uint cbBuf = (uint)strm.Length;
            factory.CreateImageFromBuffer(pbBuf, cbBuf, BufferDisposalFlag.BufferDisposalFlagNone, out imagingResource);
        }

private void Form1_Paint(object sender, PaintEventArgs e)<br />
        {<br />
            // We are going to double buffer to cut down on flicker.<br />
            // This isn't foolproof on slower devices (we can see the fullscreen Blt).<br />
            // You could trade space for speed and keep this background buffer around<br />
            // rather than (re)creating it each time Paint is called.  I would hook Resize and<br />
            // create a new back buffer in that event.<br />
<br />
            // The bitmap needs to be created with the 32bpp pixel format for the IImage to do the right thing.<br />
            if (backBuffer != null)<br />
            {<br />
                // We beed a Graphics object on the buffer to get an HDC<br />
                using (Graphics gxBuffer = Graphics.FromImage(backBuffer))<br />
                {<br />
                    // Since we nop'd OnPaintBackground, take care of it here<br />
                    gxBuffer.Clear(this.BackColor);<br />
<br />
                    // Ask the Image object from Imaging to draw itself.<br />
                    IntPtr hdcDest = gxBuffer.GetHdc();<br />
                    Rectangle dstRect = new Rectangle(100, 100, 148, 148);<br />
                    imagingResource.Draw(hdcDest, ref dstRect, IntPtr.Zero);<br />
                    gxBuffer.ReleaseHdc(hdcDest);<br />
<br />
                    // AlphaBlend takes two HDC's - one source and one destination.  Here's the source.<br />
                    using (Graphics gxSrc = Graphics.FromImage(constantAlphaImage))<br />
                    {<br />
                        IntPtr hdcDst = gxBuffer.GetHdc();<br />
                        IntPtr hdcSrc = gxSrc.GetHdc();<br />
                        BlendFunction blendFunction = new BlendFunction();<br />
                        blendFunction.BlendOp = (byte)BlendOperation.AC_SRC_OVER;   // Only supported blend operation<br />
                        blendFunction.BlendFlags = (byte)BlendFlags.Zero;           // Documentation says put 0 here<br />
                        blendFunction.SourceConstantAlpha = (byte)vScrollBar1.Value;// Constant alpha factor<br />
                        blendFunction.AlphaFormat = (byte)0;                        // Don't look for per pixel alpha<br />
                        PlatformAPIs.AlphaBlend(hdcDst, 36, 36, 128, 128, hdcSrc, 0, 0, 128, 128, blendFunction);<br />
                        gxBuffer.ReleaseHdc(hdcDst);    // Required cleanup to GetHdc()<br />
                        gxSrc.ReleaseHdc(hdcSrc);       // Required cleanup to GetHdc()<br />
                    }<br />
<br />
                    // Ask the Image object from Imaging to draw itself.<br />
                    /*IntPtr*/ hdcDest = gxBuffer.GetHdc(); // This is redundant, but keeps the necessary code together<br />
                    /*Rectangle*/ dstRect = new Rectangle(4, 4, 132, 132);<br />
                    imagingImage.Draw(hdcDest, ref dstRect, IntPtr.Zero);<br />
                    gxBuffer.ReleaseHdc(hdcDest);<br />
                }<br />
<br />
                // Put the final composed image on screen.<br />
                e.Graphics.DrawImage(backBuffer, 0, 0);<br />
            }<br />
            else<br />
                e.Graphics.Clear(this.BackColor);<br />
        }<br />