Re: [Openexr-devel] Embedding ICC profiles in OpenEXR

[Kai-Uwe Behrmann]

Geraldine,

a profile can be created on the fly out of the exr primaries and back 
written from the same on the fly created ICC profile into the OpenEXR 
header. CinePaint obtained such a small layer recently based on lcms. The 
same is possible with TIFF and I think as well with PNG.

Only it seems not an good solution to me to open an second path for 
describing colour characteristics in parallel if not realy needed.

Of course if OpenEXR could hold an API to convert from exr primaries to 
ICC and accepting an ICC profile to convert to its native header format, 
that would be great.

Saving of device characteristics for HDR devices is not covered by the ICC 
standard. Where there practical suggestions to hear at Scottsdale 
regarding ICC and HDR device characterisation?


regards
Kai-Uwe Behrmann
                                + development for color management 
                                + imaging / panoramas
                                + email: address@hidden
                                + http://www.behrmann.name


Am 21.11.05, 07:44 -0500 schrieb 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