[Graeme Gill]

Originally Posted by e-t172

I don't know about web browsers, but software like Photoshop seems to be able to apply an ICC profile with no perceivable delay.

There's quite a difference between concatenating the pre-built ICC A2B and B2A tables and then crunching the pixels with the resulting link, vs. creating the B2A table by inverting the A2B with any accuracy and/or computing a sophisticate gamut mapping.

And it would be pretty ludicrous to say that professional image editing software like Photoshop do this in subpar quality. In fact people using Photoshop probably care even more about color accuracy than videophiles.

Yes and no. Photoshop takes a great deal of care in applying ICC profiles, but has nothing to do with the accuracy of the profiles themselves. It just uses the ICC tables. For instance, it doesn't try and improve on the accuracy of the A2B and B2A tables re-computing B2A lookup or computing profile pair specific gamut mappings in the manner than collink is capable of.

As for "3DLUTs are not just slow for fun", well, it might be that programs like ArgyllCMS's collink command are slow because there is no perceived need to make them fast: people use it offline and very infrequently, no one cares a great deal about how long it takes.

Oh boy - I think if I added it all up, I've spent years of my time working on the performance of elements that make up collink, from profile inversion to gamut mapping. There's no doubt that there are faster ways of doing less complex gamut mapping or lower accuracy profile inversion, and of course there are almost certainly speedups possible to my current code, but its not slow for want of caring nor effort.

I suspect it would be possible to do it much faster with little loss in quality if one were to specifically optimize for that. (Does anyone know how long LittleCMS takes to generate a transform?)

Go right ahead - optimize away!

Note that collink will link profiles in simple mode in comparably short times to lcms and Photoshop though.