Re: [Gimp-developer] lcms high bit depth update: getting closer, but undo doesn't work

I'm not suggesting a hack. I'm using modified vs unmodified babl files
as a diagnostic tool.

If something works when the babl file *is* modified to eliminate the
back and forth conversions, and doesn't work when the babl file
*isn't* modified, that suggests that some bit of Gimp code - code that
is not inside the lcms.c plugin itself - is calling those babl files
*during* the ICC color space conversion process.

I wanted to know which babl functions are being invoked in "case A -
the babl files are *not* interfering with the ICC profile color
conversion process (8-bit and 16-bit integer)" compared to "case B -
the babl files *are* interfering with the ICC profile color conversion
process (indexed and 32-bit floating point)".

So I added write statements to the babl "model-rgb.c" functions and to
the "lcms.c" plug-in functions, to locate where indexed and 32-bit
floating point color conversions (which *don't* work unless the babl
file is modified) and 8-bit/16-bit integer color conversions (which
work *without* modifying the babl file) diverge in the model-rgb.c
babl functions that are called during the color conversion process.

Hopefully the resulting terminal output will be useful in tracking
down which Gimp functions (not lcms.c functions) are calling which
babl functions during the ICC profile conversion process.

On 11/23/12, Øyvind Kolås <pippin gimp org> wrote:
> On Sat, Nov 24, 2012 at 10:33 AM, Elle Stone <l elle stone gmail com>
> wrote:
>> some changes are made to either babl/babl/base/util.h or to
>> babl/babl/base/model-rgb.c. With the modified babl file, the color
>> conversions work for single layer, multiple layers, with and without
>> masks, and with and without alpha channels.
> As said earlier such changes in babl are non-sensical, and applying
> such hacks in babl will only mask issues elsewhere ;). The issues
> being masked will be issues where GIMP is using the _wrong_ Babl
> formats (linear vs sRGB gamma) for buffers.
> /Øyvind K.
> --
> «The future is already here. It's just not very evenly distributed»
>                                                  -- William Gibson

Elle Stone - articles on open source digital photography

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