[Bf-vfx] OCIO branch

[Lukas Tönne]

Hi,

I have recently updated the existing OCIO branch [1] by Xavier Thomas
to latest trunk (last update was 8 months ago) and put a copy in my
personal git repository [2]. After discussion with Brecht i've made a
few changes to the code layout and done some minor work to make myself
familiar with the C API and OCIO in general. Check the log [3] for
details (i'll keep the branch rebased on trunk, so the commits will
stay on top). I have no background in color management, so please bear
with me and correct me if i'm wrong :)

Coder stuff:

One general design question is how to handle display buffers. I think
the consensus is that all float image buffers should generally be
using scene-linear profiles. In order to display such buffers using
the current glDrawPixels methods (GLSL transformation may work using a
shader) i assume it is preferable to use a cached display buffer with
the color-transformed ("sRGB") values. UI elements with single or
limited number of colors OTOH can probably use direct color
transformation calls for drawing.

The only place where such a display buffer is implemented atm is the
Image space, which uses a second ImBuf struct "colormanaged_ibuf" to
store the display device values. In other places the scene-linear
buffer may not even be stored (point in case: node previews), so the
image would have to be reconstructed (compositor/shader execution)
each time the display/view profile is changed ...

My suggestion would be to add the display buffer directly in the ImBuf
struct, in addition to the original scene-linear rect_float (for int
buffers this would just be the unsigned char *rect buffer). ImBuf
should generally be used in all places where image data is displayed
in the UI (so node preview would use it as well). Does that make
sense?

Regards,
Lukas

[1]
https://github.com/thmxv/blender-ocio

[2]
https://www.gitorious.org/~lukastoenne/blenderprojects/blender-lukastoenne

checkout the branch directly with:

git clone git://gitorious.org/~lukastoenne/blenderprojects/blender-lukastoenne.git
-b ocio

[3]
https://www.gitorious.org/blenderprojects/blender-lukastoenne/commits/ocio