Making v2 profiles
While ICC recommends the use of v4 profiles wherever possible, it recognizes that v2 profiles continue to be used in some workflows and can give good results. It is possible to minimize the possibility of unexpected results or inconsistent quality by adopting v4 features where possible when building v2 profiles. In practice this means:
- Use the immediate previous major revision v2 specification rather than older v2 versions.
- Use the v4 Perceptual Reference Medium Gamut in the Perceptual rendering intent to ensure consistent mapping between source and destination gamuts.
- Ensure that the computation steps applied to populating the mediaWhitePointTag of each profile are consistent with the clarified wording in the v4 specification. In display profiles, set the medium white point to D50 and apply chromatic adaptation and white point scaling (only) as for v4 profiles. Any desired black point scaling should be performed by the CMM.
- Ensure that Colorimetric intents are measurement based and do not include preference adjustments.
- Ensure that AToB transforms accurately invert the corresponding BToA transforms in the profile.
- Populate the profileID field in the profile header as specified for v4.
To avoid inconsistent results where v2 profiles are used in workflows where both v2 and v4 profiles may be encountered, it is also recommended that optional tags in the v2 specification that have subsequently become obsolete are not included in future profiles made to the v2 specification. These tags are:
When designing workflows for v2 and v4 profiles, it is important that colour processing does not produce different results according to whether these tags are present or not.
Where profile creators wish to retain the functionality provided by these deprecated tags, for example to include screening and black generation information in the profile, an alternative is to use the new Dictionary Type and Metadata Tag. The dictType tag has been approved for v2 profiles, and can be used to encode additional context information into the profile.
V4 raison d'etre to enable intelligent CMMs and improve results for non-linear color spaces contains the V2 - V4 technical changes and benefits list.
Some common problems with v2 profiles that fail to conform to the v2 specification are listed here.