[cairo] Trouble resizing (scaling) an XImage

[Uli Schlachter]

On 27.06.2011 17:00, Justin Anderson wrote:
>    //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);

I hope you are waiting for an Expose event before actually trying to draw
something? (Or alternatively you aren't running any window manager)

>    //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);

In another mail you said:
> I should mention that the source image is an 8 bit grayscale.  Thanks.

So where is CAIRO_FORMAT_RGB24 coming from?

>    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);

Where is this coming from? You are first drawing something with cairo and then
using XPutImage() to "overwrite" the result?

>    cairo_surface_destroy(surface_dest);
>    cairo_surface_destroy(surface_source);



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- Three months ago. I woke up one morning married to a pineapple.
  An ugly pineapple... But I loved her.