GdkBitmap structure - 3 questions

["Germano Rizzo" <manomano ciaoweb it>]

Hi!
    In my program I use gdk-pixbuf; actually I'm using some bitmaps, loaded
from the alpha channel of some PNG files. Now, I'd have to do three things:
- have the possibility to 'negative-image' them; now I'm using two different
files for a bitmap and its negative... I guess there should be a way!!
- have the possibility to merge two of them (e.g copying one into another
one, then 'painting' the white areas of another into it)

    In other words, is there any direct access to the pixel, to be able to
scan them and modify 'on the fly'? I'm not bothered with performances, they
would be only 3 or 4... and again:

- how can I load *directly* a bitmap from a 1-bit PNG file? Actually I'm
using alpha channel because the relative function is the only one that gives
back a GdkBitmap; when I try to use the rendering functions that gives a
GdkDrawable with a GdkBitmap, and use this last one to shape a window, the
program exits and says the bitmap is bad...

    Thank you,
        Mano :)

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