setting a transparent color on a pixbuf for Canvas layering

[zentara <zentara1 sbcglobal net>]

Hi,

This question came up today on perlmonks, and it
sort of piqued my interest. It concerned laying a radar
weather map over a ground map.

The idea was to layer the radar map over the ground map,
setting a background transparency on the radar map.

Well, I could do this with GD, as shown in the attached script
GD-transparency-add.  It has a simple 
$gd->transparent($green); 
to set green as transparent.

So I used this script to change the green section of zzrgbwb.png
to transparent, as zzrgbwb-gt.png.

Then I load that transparent overlay over a basefile of your choice
in the script transparent2,

Now the REAL question is "How to do this with Gtk2's pixbuf and Image
methods?"

How do I take the non-transparent zzrgbwb.png , load it with Gtk2, and
make green transparent without resorting to GD?


Thanks, 
zentara



-- 
I'm not really a human, but I play one on earth.
http://zentara.net/CandyGram_for_Mongo.html

Attachment: GD-transparency-add
Description: Binary data

Attachment: zzrgbwb.png
Description: PNG image

Attachment: zzrgbwb-gt.png
Description: PNG image

Attachment: transparent2
Description: Binary data