[Gimp-developer] Displaying linear gamma images (Was Re: Update on my Gimp color management coding efforts)

[Elle Stone <l elle stone gmail com>]

On 11/12/12, Elle Stone <l elle stone gmail com> wrote:
> On 11/10/12, Michael Natterer <mitch gimp org> wrote:
> > On Sat, 2012-11-10 at 15:17 -0500, Elle Stone wrote:
> > > On 11/8/12, Jon Nordby <jononor gmail com> wrote:
> > > > * Change the lcms-based conversion (modules/display-filter-lcms.c)
> > > > from being a generic display filter to be something that takes a
> > > > GeglBuffer in and blits into a cairo_surface_t.
> > > > * Change the display filter interface to accept a GeglBuffer instead
> > > > of a cairo_surface_t. As gimp_color_display_convert_surface is public
> > > > API, it should probably become a stub and be marked as deprecated. New
> > > > interface could for instance be called
> > > > "gimp_color_display_convert_buffer"
> > > > * Adapt all the display filter operations (modules/display-filter-*.c)
> > > > to the new interface and to working on 32bit floating point. If any of
> > > > the operations are no longer useful, now would be the time to drop
> > > > them.
> > > > * In the use of the display filter stack (in
> > > > gimp_display_shell_render), first let the filter stack operate on the
> > > > GeglBuffer from the projection (or possibly a copy), and then pass it
> > > > to the lcms-based color conversion, and then pass that to cairo.
> > > I'm looking forward to taking another look at the monitor display code
> > > path. Your suggestions sound very helpful.
> >
> > It does, but it's clearly step 2 (or step n). IMO we should first
> > get the lcms plug-in right so the data GIMP is dealing with is
> > correct in the first place.

Step 1 happened a long time ago. I'm trying to implement Jon Norby's
suggestions because it would be nice to see a linear gamma image
displayed without posterization in the shadows from the conversion to
8-bits that happens before the conversion to the monitor profile.
Quoting Jon's suggestion:

(1)call a "GeglBuffer from the projection (or possibly a copy)" and then
(2)pass it to the lcms-based color conversion, and then
(3)pass that to cairo.

So how does one "call a GeglBuffer from the projection"?

Elle