gdk_pixbuf_composite_color() issue resolved..

[Dave Andruczyk <djandruczyk yahoo com>]

I got it to work. Went back to using GtkImage.  Seems the problem was caused by
how I loaded the file originally.  The file load killed the alpha channel for
some reason,  don't really care why as now I have it working. It was my own
fault originally, as I'm 99% sure I used the wrong function or func args, I
know that...  By using gdk-pixmap-csource to convert my .png file into a header
and load that into a pixbuf and feed that into GtkImage it works great.  Thanks
for the help...




> Date: Tue, 26 Aug 2003 13:08:43 +1200
> From: Tim Evans <t evans aranz com>
> Organization: Applied Research Associates NZ Ltd
> To: gtk-app-devel-list gnome org
> Subject: Re: gdk_pixbuf_composite_color()  help needed.
>
> This is a multi-part message in MIME format.
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>
>  >> Why not just create a GtkImage widget and use that to display your
> > > pixbuf?  GtkImage is a subclass of GtkMisc, just like GtkLabel, so 
> > > it's basically a label that displays an image instead of some text. 
> > > Use gtk_image_new_from_pixbuf to easily create the widget and set it
> > > to display your pixbuf.
> >
> > I did that originally,  but the logo has an alpha channel and a 
> > gentle fade at the edges,  since X11 doesn't natively handle alpha 
> > channels, the GtkImage clips it and make the logo look like crap. 
> > (sharp edge) By compositing it with the color of the background it 
> > has a nice smooth transition,  the problem comes with getting the 
> > background color in the same format that gdk_pixbuf_composite_color 
> > accepts (I get the color back in 16 bit,  the gdk call wants it in 
> > packed 8 bit,  the resolution loss causes errors and leaves unwated 
> > artifacts onscreen.
> >
> > If I could find the code to actually take a screenshot of the empty 
> > space on my app before the pixmap is placed and use that as my 
> > compositing source, that would solve all of my problems.  Thus far I
> > haven't figured out how to do that.
>
> The attached screenshot shows a GtkImage displaying a png image with an 
> alpha channel (the glade icon).  The shadow on the icon is an alpha 
> channel and the GtkImage widget renders it correctly.  The code (in 
> Python) was:
>
> import gtk
> w = gtk.Window()
> i = gtk.Image()
> i.set_from_file('glade.png')
> w.add(i)
> w.show_all()
> gtk.main()
>
> Perhaps you need to upgrade your version of GTK, I'm using 2.2.2

=====
Dave J. Andruczyk

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