[cairo] Trouble resizing (scaling) an XImage

[Justin Anderson]

Hello,

I'm trying to resize an X11 XImage which is a 640x480 pixel image from a
video grabber, to be displayed on a window in an X11/Motif application.

If I comment out the scale command in the following code, the image is
displayed fine, albeit clipped on my window.  If I uncomment the scale
operation, there is no image in the window.

Any ideas?  Thanks!



   //Create a simple X11 window for displaying the XImage...
   window = XCreateSimpleWindow(
      display,
      RootWindowOfScreen(screen),
      0, // x
      0, // y
      width,
      height,
      0,                          // border width
      BlackPixelOfScreen(screen), // border
      BlackPixelOfScreen(screen)  // background
   );
   XMapRaised(display, window);

   //cairo stuff...
   cairo_surface_t *surface_dest = cairo_xlib_surface_create(display,
window, XDefaultVisualOfScreen(screen), width, height);
   cairo_t *cr_dest = cairo_create(surface_dest);

   cairo_surface_t *surface_source =
cairo_image_surface_create_for_data((unsigned char*)(xImage->data),
CAIRO_FORMAT_RGB24, xImage->width, xImage->height, xImage->bytes_per_line);

   cairo_scale(cr_dest, width / xImage->width, height / xImage->height);

   cairo_set_source_surface(cr_dest, surface_source, 0, 0);
   cairo_paint(cr_dest);
   cairo_surface_destroy(surface_source);

   //Put the scaled XImage on the window...
   XPutImage(display, window, gc, xImage, 0, 0, 0, 0, width, height);
   cairo_surface_destroy(surface_dest);
   cairo_surface_destroy(surface_source);
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