I have a routine which uses the GDI to display an image using '.DrawImage'.

Sections of the image have been made transparent using '.MakeTransparent'.

Everything works well...

....BUT, I later need to replace the original image with a second image, also
with some transparent sections and cannot seem to find a way to do this.  If
I merely use 'DrawImage to write the new image, sections of the old image
show through where the new image is transparent.

I have tried putting both images in Rectangles, and manipulating the
rectangles, but this doesn't seem to work either.

I tried to find a way to capture (and then restore) the original background
on the screen before the first image was drawn, but don't think this is
doable, and if it is I cannot find how to do it in the literature.

Any GDI experts out there that can give me a hint as to how to get rid of
the original image altogether? I can't just overwrite it with an image of
the background color (unless I can capture it in realtime before I start
drawing) as this may vary (particularly under XP where the background screen
has gradients)

Regards

Glyn J Meek

Check out this FAQ about how to take a screenshot using GDI+

http://www.syncfusion.com/FAQ/WinForms/FAQ_c73c.asp#q625q
*******Reprinted for convenience**************
C#]
     internal class NativeMethods
     {
          [DllImport("user32.dll")]
          public extern static IntPtr GetDesktopWindow();

          [System.Runtime.InteropServices.DllImport("user32.dll")] 
          public static extern IntPtr GetWindowDC(IntPtr hwnd);

          [System.Runtime.InteropServices.DllImport("gdi32.dll")]
          public static extern UInt64 BitBlt
               (IntPtr hDestDC,
               int x,
               int y,
               int nWidth,
               int nHeight,
               IntPtr hSrcDC,
               int xSrc,
               int ySrc,
               System.Int32 dwRop); 
     }

          // Save the screen capture into a jpg
          public void SaveScreen()
          {
               Image myImage = new
Bitmap(Screen.PrimaryScreen.Bounds.Width,
                   Screen.PrimaryScreen.Bounds.Height);
               Graphics gr1 = Graphics.FromImage(myImage);
               IntPtr dc1 = gr1.GetHdc();
               IntPtr dc2 =
NativeMethods.GetWindowDC(NativeMethods.GetDesktopWindow());
               NativeMethods.BitBlt(dc1, 0, 0,
Screen.PrimaryScreen.Bounds.Width,
                    Screen.PrimaryScreen.Bounds.Height, dc2, 0, 0,
13369376);
               gr1.ReleaseHdc(dc1);
               myImage.Save("screenshot.jpg", ImageFormat.Jpeg);
          } 
*********************

Hope that helps,
Joel Martinez
Orlando .NET User Group
http://www.onetug.org
http://www.codecube.net


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