Re: gdk_pixbuf questions

Hello Havoc,

thank you for your fast answer :-)

On Sun, Mar 30, 2003 at 04:11:16PM -0500, Havoc Pennington wrote:
> It depends on the return of gdk_pixbuf_get_colorspace() and
> gdk_pixbuf_get_n_channels(), though at the moment the only possible
> values are RGB and RGBA.
Ok, I will add something like an assert to my code,
just to make sure.

> > (1) What is a portable way to access the alpha values of a pixbuf?
> > Does something like
> > 
> >     pixels = gdk_pixbuf_get_pixels(pixbuf);
> >     alpha = pixels [ 4*(y*width + x) + 3 ];
> > 
> > always work, or does this depend on the byte order?
> It doesn't depend on byte order, 
This is nice to hear.

> but you need rowstride instead 
> of width, and you need to be sure the pixbuf has an alpha channel.
Yes I knew this, but I wanted to keep my example simple.

> 0x000000FF is always opaque black. It's defined as 
> R << 24 | G << 16 | B << 8 | A I believe.
This is nice, too.  Maybe something like this could
be added to the gdk_pixbuf API reference?  Should I file
a wishlist bug?

Thank you again,

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