hi, not sure if i've gotten the wrong end of the stick, here, but i've solved this with the following logic: renderer = gdk_pango_renderer_get_default(); gdk_pango_renderer_set_drawable(renderer, window); gdk_pango_renderer_set_gc(GC); context = gtk_widget_create_pango_context(); desc = pango_font_description_from_string(); layout = pango_layout_new(context); pango_layout_set_text(layout, "string to display", -1); pagno_layout_set_font_description(layout, desc); gdk_draw_layout(pixmap, gc, xpos, ypos, layout); g_object_unref(layout); the original poster essentially said the same thing (render to a pixmap first), except i don't have a problem with the background, it's correct (settable by the user, so no hard-codedness). cheers, richard boaz > > > ------- Forwarded message ------- > From: "Chris Seaton" <chris@xxxxxxxxxxxxxxx> > To: Frédéric Terraza <fterraza@xxxxxxx>, gtk-list@xxxxxxxxx > Subject: Re: Trying to draw text on a pixbuf > Date: Sat, 10 Sep 2005 18:02:47 +0100 > > I was doing this a while ago. > > Specifically, I was using Pango to create text for OpenGL textures, but > I needed to have rendered text with an alpha channel to do that, just > like you do. > > Pango is pretty shit in that it won't (as far as I can tell) render an > alpha channel. I mean how basic is that? > > You can't just render onto a black background and then set black to be > transparent, as remember that the text could be antialised. > > What I did was to render white text on a black background into a pixbuf, > add an alpha channel (there's a function for that) then itterate through > each pixel in the pixbuf, copying the red channel into the alpha channel > (remember we rendered white on black, so the text will be opaque and the > background transparent), and then setting the red green and blue > channels to be whatever colour I wanted. > > You can then render that pixbuf. > > There will be some very slight artifacts does to sub pixel > antialisiaing, so I wouldn'e be writing GIMP's text tool using this. > Anyone not knowledgeable about antialiasing will probably not notice it > though. > > Chris > > Frédéric Terraza wrote: >> Hello, >> this is my first post ever on a mailing-list, I hope I'm doing it the >> right way. My apologies if not so. >> I'd like to draw text on a pixbuf. I first tried : >> - to write text in a PangoLayout >> - to render the layout in a pixmap >> - to copy the pixmap in the pixbuf >> It worked, but the text has a black background that overlap the >> previously drawn things on the pixbuf. And I can't change the background >> color (with a gdk_gc_set_background for example). >> So, I tried : >> - to render the pixmap in a temporary pixbuf >> - to add alpha to this pixbuf, making black become transparent >> - to copy this temporary pixbuf in my final pixbuf. >> Same results. And I don't know why. >> Maybe alpha isn't taken into account by gdk_pixbuf_copy_area ? If so, I >> suppose it's not too hard to make another version of this primitive >> doing that (but slow). >> And since it bothers me to have black as background color (what will I >> do if the foreground color is also black ? It may happen with text), do >> you have an idea for how to change the background color ? >> Thanks in advance. And excuse my english, school is far away now... >> Fred >> _______________________________________________ >> >> gtk-list@xxxxxxxxx >> http://mail.gnome.org/mailman/listinfo/gtk-list >> > > _______________________________________________ > > gtk-list@xxxxxxxxx > http://mail.gnome.org/mailman/listinfo/gtk-list > > > > -- > Richard Boaz > riboaz@xxxxxxxxx > +31.(0)648.792.484 > http://www.boazconsultancy.com > _______________________________________________ gtk-list@xxxxxxxxx http://mail.gnome.org/mailman/listinfo/gtk-list
