Marti Maria schrieb:
It currently uses ICC encoding, either v2 or v4 on depending on the version of the Lab profile being used as input/output.
Marti,
I've now also looked at the code. For me it looks like UnrollLabDouble() converts TYPE_Lab_DBL to either V2 or V4 PCS encoding (as you said), depending on "lInputV4Lab". But I could not find, where this variable is actually set - so it seems to be always FALSE, and thus TYPE_Lab_DBL is always converted to V2 encoding. On the other hand, TYPE_Lab_8 seems to be converted to 16-bit by multiplication with 257 in RGB_8_TO_16(), called from Unroll3Bytes(), i.e. TYPE_Lab_8 seems to be converted always to the 16-bit *V4* PCS encoding. Now I'm a bit confused. Why is Lab_DBL always convert to V2, and Lab_8 always to V4 encoding? Did I miss something?
Concerning the API: Shouldn't cmsDoTransform() rather hide the used profile version from the API, and use a Lab_16 encoding at the API which is *independent* of the used profile? As user of the API I rather don't want to need to care, which profile version I'm using. May I suggest, that the API should provide either TYPE_Lab_16_V2 or TYPE_Lab_16_V4 (or both), and convert to the actual profile's encoding internally if necessary.
Btw, I'm also a bit confused about the ICC spec. The V4 spec defines the new 16-bit CIELAB PCS encoding in Annex A. But even with V4 profiles, the lut16Type CLUT tables still use the old V2 16-bit CIELAB PCS encoding, this is explicitly mentioned in the spec. So where is the new V4 PCS CIELAB encoding actually used? Is ist used for the PCS side of the new lutAtoBType, ... tables? (I guess so, but I couldn't find a definite statement in the spec)
Best Regards, Gerhard
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