Re: alpha for text?

[John Cupitt <jcupitt gmail com>]

Hi again,

On 7/16/05, Paul Pogonyshev <pogonyshev gmx net> wrote:
> John Cupitt wrote:
> > On 7/15/05, Paul Pogonyshev <pogonyshev gmx net> wrote:
> > > Has anyone rendered text with alpha channel (i.e. semitransparent text)
> > > in GDK framework?  So far my best solution is to render black on white
> > > to a GdkImage, get it back in a GdkPixbuf and then add color/transparency
> > > manually.  Not actually too difficult, but I want to ask in case somebody
> > > can come up with something better.
> >
> > You can use pangoft2 to render text on the client side and thereby
> > avoid shipping images back from the server. Not much neater, but quite
> > a bit quicker.
>
> Can I have a little more information here, please?  I thought GtkImage was
> client side.  And if not, is your approach portable all the way back to
> GTK+ 2.0?

I hope I'm not misunderstanding you here (apologies if I am), but I
think it sounds like you are rendering text to an off-screen pixmap
with gdk_draw_layout(), fetching to the client as a GdkImage, then
going to a gdkpixbuf to manipulate it. The gdk_draw_layout() is
probably rasterising the font with freetype2 client-side, then
shipping the rendered glyphs to the server. So you may well be sending
the data both ways.

If you've not seen it, have a look at pangoft2topgm.c in the pango
sources. It's a command-line program which renders text directly to a
bitmap (with no X server) using pangoft2. I used this as a base for a
text render operation in my image processing library with great
success. As far as I know, this will work on any gtk+-2.0, though I've
not tested it.

John