Fwd: [cairo] how to use alpha blending by cairo?

[Carl Worth]

On Thu, 13 Jul 2006 13:53:07 +0530, Rajeev wrote:
> Now is there a work around for adding all channels(say, an alpha
> channel) of an image with cairo ??

You can, for example, use cairo_paint_with_alpha rather than
cairo_paint, for example, here perhaps:

>         gdk_cairo_set_source_pixbuf (cr, pixbuf, 0, 0);
>         cairo_paint(cr);

The cairo_paint_with_alpha function is a convenience function for the
much more general cairo_mask function which allows you to draw a
source through any mask you like. So paint with alpha simply creates a
mask with a uniform alpha value and then calls cairo_mask for
you. With calling cairo_mask directly you can do things such as using
a radial alpha gradient as the mask.

-Carl
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