Re: Alpha transparency in Image.

["John Hobbs" <john velvetcache org>]

I don't know about that way, but you could try doing it with Cairo,
thats worked for me before.

bool on_expose_event (GdkEventExpose * ev) {
    Glib::RefPtr<Gdk::Window> window = drawOnMe.get_window();
    if(window) {
        Cairo::RefPtr<Cairo::Context> context = window->create_cairo_context();
        // Shoehorn the image data into the context, then render it.
        Cairo::RefPtr<Cairo::ImageSurface> image_surface =
Cairo::ImageSurface::create (Cairo::FORMAT_RGB24, img_->get_width(),
img_->get_height());
        Cairo::RefPtr<Cairo::Context> image_context =
Cairo::Context::create(image_surface);
        Gdk::Cairo::set_source_pixbuf (image_context, img_, 0.0, 0.0);
        image_context->paint();
        context->set_source(image_surface, 0.0, 0.0);
        context->paint_with_alpha(0.5);  // The param here is your alpha value
    }
}

- John Hobbs

On Thu, Aug 14, 2008 at 2:21 PM, Germán Diago <germandiago gmail com> wrote:
>  I want to set the alpha transparency of an image with this code, but
>  it does nothing.
>  Could anyone tell me the correct way to do it?
>
>
>  bool on_expose_event(GdkEventExpose* ev)
>        {
>                img_->add_alpha(false, 0, 0, 0);
>                img_->composite(img_, 0, 0, img_->get_width(),
> img_->get_height()
>                                                        , 0, 0, 1, 1,
> Gdk::INTERP_BILINEAR, 10);
>                img_->render_to_drawable(get_window(),
> get_style()->get_black_gc(),
>                0, 0, 100, 80, img_->get_width(), img_->get_height(),
> // draw the
>  whole image (from 0,0 to the full width,height) at 100,80 in the
>  window
>                Gdk::RGB_DITHER_NONE, 0, 0);
>                return true;
>        }
>
>  img_ is a Glib::RefPtr<Gdk::Pixbuf>.
>
>  Thanks in advance.
> _______________________________________________
> gtkmm-list mailing list
> gtkmm-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtkmm-list
>