On Mon, 2007-10-15 at 09:04 -0700, Carl Worth wrote: > On Sat, 13 Oct 2007 00:51:44 +0000, "=?ISO-8859-1?Q?BJ=F6rn_Lindqvist?=" > wrote: > > I have played around with Cairo some more and it seems to me that it > > is not fully ready yet. :( Cairo blits and scales much slower than > > gdk-pixbuf (software that is) > > Do you have some simple test cases to demonstrate this so we can > identify and fix anything necessary in cairo?
This would be a pretty interesting benchmark. Any takers? :) > > and doesn't support as good-looking bilinear filtering that > > gdk-pixbuf does. > > The scaling code in cairo, (for downscaling by factors greater than > 2), could definitely use some improvement, (the current result is > embarrassingly ugly). But what GdkPixbuf does here is actively bad for > performance. I'd like to see some middle-ground implementation. GdkPixbuf's scaling functions provide *very* nice results when downscaling with GDK_INTERP_BILINEAR, though they are slow as you say. High quality, but slow (for "slow" == "way slower than no interpolation", or "I can't do 30 FPS for an image the size of my whole screen"). I don't really know if there is a good, general solution for this. There are several cases: - Downscaling things once, like when generating a bunch of thumbnails or scaling down big-wallpaper-1600x1200.png into something that fits in your puny 1024x768 screen. There's not much you can do here except profiling the heck out of your one-time scaling algorithms. - Downscaling things continuously, say, when interactively zooming in an image viewer. A stateful mip-map would help here, so you don't have to recompute everything on every change of scale. Note that you can play tricks here: EOG's beautiful zooming comes from doing a quick atomic pass with no interpolation, and then doing bilinear interpolation of small tiles in an interruptible fashion. - People forget that "high quality rendering" and "good performance" are at opposite sides of the scale :) High-quality downscaling simply requires you to look at a lot of source pixels to generate each destination pixel. Often people want to replay trivial code in their repaint functions, such as taking a huge image, downscaling it, and painting it. It's better to scale image *once* and then reuse the result when you repaint. That makes the program's logic more complicated, but that's life. Federico _______________________________________________ gtk-devel-list mailing list gtk-devel-list@gnome.org http://mail.gnome.org/mailman/listinfo/gtk-devel-list
