Replace GDI+ DrawImage with PInvoked GDI and transparent PNG's

Question

I\'ve created an image service in C# which takes a base layer image (JPG), layers one more more transparent PNG\'s (32 bit), and then outputs a final JPG image. I\'m tryin

Answer 1

This one should work:

    private Bitmap GetImage() {
        //##################### Get the Bitmaps ############################
        Bitmap sourceImage = new Bitmap("c:\\1.png");
        Bitmap overlayImage = new Bitmap("c:\\2.png");

        //##################### Get Hdc from baselayer ############################
        Graphics sourceImageGraphics = Graphics.FromImage(sourceImage);
        IntPtr sourceImageHDC = sourceImageGraphics.GetHdc();

        //##################### Get Cdc from second layer ############################
        IntPtr overlayImageCDC = CreateCompatibleDC(sourceImageHDC);
        IntPtr overlayImageHandle = overlayImage.GetHbitmap();
        SelectObject(overlayImageCDC, overlayImageHandle);

        /*
         * BitBlt from sourceImage is not neccessary,
         * because Graphics.FromImage(sourceImage) already did it for you
        */

        //##################### Draw the second layer ############################
        AlphaBlend(sourceImageHDC, 0, 0, overlayImage.Width, overlayImage.Height, overlayImageCDC, 0, 0, overlayImage.Width, overlayImage.Height, new BLENDFUNCTION(AC_SRC_OVER, 0, 0xff, AC_SRC_ALPHA));

        //##################### Release everthing ############################
        sourceImageGraphics.ReleaseHdc(sourceImageHDC);
        sourceImageGraphics.Dispose();

        DeleteDC(overlayImageCDC);
        DeleteObject(overlayImageHandle);

        //##################### Return Image ############################
        return sourceImage;
    }