On 24-08-10 11:51, Øyvind Kolås wrote:
On Tue, Aug 24, 2010 at 9:58 AM, Rupert Weber<g...@leguanease.org>  wrote:
On 08/24/2010 04:20 AM, David Gowers wrote:
I hope you're not associating the quite suboptimal way in which GIMP
currently uses GEGL, with BABL's speed or lack of speed.
BABL just processes raw pixel buffers. A converter function just
accepts a source and a destination pointer, along with a pixel count,
and should convert that number of pixels. It doesn't have any heavy
architecture or processing, aside from what may be in each individual
converter function

looking at your code in gimpcolorspace.c, making that code work with
BABL looks like it's pretty much a case of cut+paste, modify the way
the input is referred to, add some registration code.

(getting your layer mode code to USE that, is a different issue, and I
agree that would be non-trivial, although you might get significant
speed gains from it because of greatly reduced function call overhead
-- probably about as much as you describe for inlining below.)
As I indicated, I'll be happy to make the babl integration of those
conversions my next little project, but I also expect a bunch of
questions to come up in the process (color management comes to mind).
Color management does not have much to do with this, since the pixels
are already assumed to be in a well defined pixel format and color
space. Babl is nothing more than a collection of conversion functions,
meta data about the color spaces and data types used and the ability
to assess the conversion speed and quality of these conversions at
runtime. Thus as long as the claim as to what pixel format a buffer is
in is correct, use of babl is correctly color managed.

/Øyvind K.
Well how well defined is the format that babl receives and sends back.

According to the web page at : http://www.gimp.org/release-notes/gimp-2.4-cm.html. The intent is to work in Gimp using the sRGB color space, however one can ignore this. On the other side there babl is supposed to work in scRGB (http://www.gegl.org/babl).

Maybe I didn't look hard enough but I didn't find a real conversion from sRGB(8bit) to scRGB(16bit), neigther in GIMP nor in babl as described in *http://www.colour.org/tc8-05/Docs/colorspace/61966-2-2NPa.pdf.*

In the babl extensions a CIE model is present, it takes as e reference white D65 while more common would be the reference white E (http://www.brucelindbloom.com). I assume that the sRGB/scRGB have reference white D50.

Has anyone an idea what is the reference white for the RGB color model in BABL or GIMP? Are the reference white and the chromaticity coordinates not missing in the BABL model?


Gimp-developer mailing list

Reply via email to