Re: [Gimp-developer] the Gimp lcms.c plug-in

[Elle Stone <l elle stone gmail com>]

I posted an update to my effort to port the lcms plugin to lcms2 and
get it to do high-bit-depth color conversions:

http://ninedegreesbelow.com/temp/gimp-lcms-4.html

Summary of current state of plugin:

It uses lcms2.
It does high bit depth conversions, but some options are not available yet.
It still uses deprecated functions.

Black point compensation flag has been temporarily removed (easy to
add back in, just haven't done it yet).

The code doesn't check for an alpha channel, and won't work if the
image has an alpha channel  (easy to add, just haven't done it yet).

The code will convert at 8-bit integer, 16-bit integer and 32-bit
floating point (only, so far).

The ICC profile conversion is seemingly correct only if the starting
profile is a linear gamma version of sRGB and the ending profile is
the Gimp built-in sRGB, or vice versa.

Upon converting to any other ICC profile, the colors come out all
wrong (confirm by opening in another application and eye-droppering).
***However***, upon:

*exporting the odd-looking image anyway (and confirming that the
numbers are wrong in another imaging application)
*closing and reopening Gimp (not a necessary step, but eliminates the
possibility of "right values" somehow being in memory)
*reopening the exported image (which still looks odd)
*and then converting it to built-in sRGB or to linear sRGB

. . . then the colors are magically right. Which is both bizarre and wrong.

Elle
-- 
http://ninedegreesbelow.com
Articles and tutorials on open source digital imaging and photography