[Openexr-devel] Half samples & DPX

[Bob Friesenhahn]

A SMPTE workgroup is currently re-working the specification for the 
venerable DPX file format.  I know that several people on this list 
have been involved in the discussion.  A new planned addition is 
support for Half samples as used by OpenEXR.  There was already 
support in the specification for storing 32 and 64 bit floats.

It seems to me that there needs to be a bit of file metadata to allow 
Half data to be exported from OpenEXR into DPX while preserving the 
original intent of the values.  DPX is a very spartan format so 
exporting a full CTL description is not a good fit.  In DPX, standard 
colorspace transforms are indicated by reference (e.g. as an 
enumeration) and non-standard transforms need to be managed (by the 
user) using an external LUT.

I am interested to hear any ideas as to what the minimal amount of 
metadata needs to be in order to support exporting an RGB(A) rendition 
of the image from OpenEXR into a simple float representation suitable 
for viewing, grading, or sending to a film printer.  Is there a 
standard Half (or floats in general) sample representation which 
allows viewing/interpreting the image without using exotic color 
management approaches like CTL?

Bob
======================================
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/