Re: cairo surface from GdkPixmap

[Dov Grobgeld <dov grobgeld gmail com>]

Hi Andrew,

See my tutorial at:

http://giv.sourceforge.net/gtk-image-viewer/gtkimageviewer_tutorial.html

and search for "cairo" for an example of how to draw on a pixbuf with cairo. Basically all you need to do is:

  cairo_surface_t *surface
    = cairo_image_surface_create_for_data(gdk_pixbuf_get_pixels(pixbuf),

                                          CAIRO_FORMAT_RGB24,
                                          img_width,
                                          img_height,

                                          gdk_pixbuf_get_rowstride(pixbuf));

Beware cairo's and gdkpixbuf's ideas about r,g, and b, are swapped so you will need to swap the blue and the red channels when painting.

Regards,
Dov

2009/6/14 Andrew Cowie <andrew operationaldynamics com>

On Sat, 2009-06-13 at 19:50 -0700, Michiel de Hoon wrote:
> I am looking for a way to obtain a Cairo surface from a GdkPixmap.

You're probably looking for gdk_cairo_create() or
gdk_cairo_set_source_pixmap(), depending on what exactly you're up to.
http://library.gnome.org/devel/gdk/stable/gdk-Cairo-Interaction.html

As is compulsory on this list :) I note in passing that it turns out
that this [poorly-named] list is the one for discussion about _hacking_
on GTK. Questions about _developing_ with the library are best directed
to gtk-list.

AfC
Sydney


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