[Openexr-devel] Embedding ICC profiles in OpenEXR

[Geraldine Joffre]

I've been to a conference on HDR-Photography and 3D-Visualisation in Hamburg 
last week. The 
audience was mainly professional photographers, so when Spheron talked about 
their HDR 
camera, they were asked about how the HDR files are color managed and whether 
they have 
ICC profiles (color management is very important for quality photography).

The answer was that the SheroCam HDR camera had been characterized but that no 
ICC profile 
is available for the HDR files produced. The only way to get an ICC profile is 
to shoot an LDR 
image so that the profile gets embedded in a 16-bit TIFF file. So, I intervened 
to explain that a 
newer version of the OpenEXR format makes it possible to define the 
chromaticities of the RGB 
primaries and white point, which means the camera just needs to populate the 
chromaticities 
attribute when writing the HDR file in order to get a 'color managed' HDRI.

However, from the discussions I had afterwards, I realized it might be more 
convenient for a 
photography workflow to have the chromaticities values available in the form of 
an ICC profile 
embedded in the OpenEXR file. The responsibility for creating and embedding the 
profile would 
be left to the application that produced the OpenEXR file -- the HDR camera or 
the software that 
created it from multiple exposures. The advantage is that the CMM of color 
managed software 
could directly handle OpenEXR files that have an embedded ICC profile. 
Otherwise, additional 
coding is necessary to extract and convert the chromaticities attribute for 
correct handling by 
the CMM. 

I think it could be a good idea to add the ability to embed ICC profiles in a 
future version of 
OpenEXR, the same way it can currently be done with the TIFF and JPEG formats.

Thanks.

Geraldine Joffre

--
HDR Imaging for Photography
http://www.hdrsoft.com