gdk-pixbuf-add-alpha

[Tomas By]

Hi all,

I am trying to change a colour to transparent by doing this:

  (gdk-pixbuf-add-alpha img #t (integer->char r) (integer->char g) 
(integer->char b))

(Doing `interger->char' seems a bit weird but passing ints causes 
errors.)

However, the image is not changed (I write it out using 
gdk-pixbuf-save-to-port).

Doing it on the command line works fine:

  convert old.png -transparent 'rgb(R,G,B)' new.png

so I am pretty sure there is no problem/misunderstanding regarding the 
file and the colours.

Anybody have any ideas how to do this in Guile?

/Tomas