[pygtk] problems with image transparency and flipping

[David Hugh-Jones]

Replying to myself, in case it is useful in future:

here is a simple function (not at all optimized, and
only works with alpha images) to flip images
horizontally:


def flip_pixbuf(pb):
        bps = pb.get_bits_per_sample()
        rs = pb.get_rowstride()
        pix = pb.get_pixels()
                                                      
                         
        newpix = ""
        x = rs
        pixstride = pb.get_n_channels() * bps/8
        while x <= len(pix):
                row = pix[x - rs : x]
                newrow = ""
                x = x + rs
                y = pixstride
                while y <= len(row):
                        sample = row[y - pixstride :
y]
                        y = y + pixstride
                        newrow = sample + newrow
                newpix = newpix + newrow
                                                      
                         
        return gtk.gdk.pixbuf_new_from_data(newpix,
pb.get_colorspace(), \
                        pb.get_has_alpha(), bps,
pb.get_width(), \
                        pb.get_height(), rs)



If anyone can explain how to copy one pixbuf to
another, using a clip mask, I would be very pleased.

David


--- David Hugh-Jones <hughjonesd at yahoo.co.uk> wrote: >

> Hi All
> 
> I have been using pygtk2 for some simple image
> manipulation. It's very nice, but I have two
> problems/questions that maybe someone can help with:
> 
> 1. How can I flip a gtk.PixBuf image? I read an
> earlier message saying that this is "just a trivial
> manipulation of the buffer" - can someone tell me
> how
> a PixBuf buffer is structured?
> 
> 2. I have a PixBuf created from a transparent PNG
> (with an alpha channel). When I do
> 
> pixbuf.copy_area(background, ....)
> 
> the pixbuf is copied on to background, but the
> transparency is rendered as a grey square. How can I
> make sure that the transparency gets rendered
> properly?
> 
> Thanks very much for all replies.
> 
> David Hugh-Jones
> 
> 
> 
> 
> 
> 	
> 	
> 		
>
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