Re: Crash when calling Gdk::Drawable::draw_pixbuf

[Chris Vine <chris cvine freeserve co uk>]

On Sat, 20 Jun 2009 13:33:12 +0200
Falk Schilling <falk schilling gmx net> wrote:
[snip]
> Thank you for this clarification. My whole experience with GTKMM/GTK+
> relates to only a few weeks, so I am far away from understandig the
> whole complexity of all part libraries.

This will explain how the image data in Gdk::Pixbuf/GdkPixbuf is set
out:
http://library.gnome.org/devel/gdk-pixbuf/stable/gdk-pixbuf-gdk-pixbuf.html#image-data

Note that, unlike cairo image surfaces, the alpha value (if any) of the
pixel data in Gdk::Pixbuf is lossless and not premultiplied, so you
need to do a conversion were you to want to convert between the two
(cairo uses premultiplied alpha and the RGB pixel data is stored
differently, in 32 bit integers). Cairo is more efficient in
interfacing with the Xserver because of its pixel layout, and in
compositing. Gdk::Pixbuf is usually easier to manipulate on the client
side at the pixel level.

Chris