Hi! Dare I even ask why people are writing PNG files from Nuke? It's not > exactly a VFX-friendly file format. >
In this case we use Nuke to prepare production assets for webreviews and distribution. > You can force some kind of conversion with oiiotool. If you have a file > that saves as PNG but that somehow you know is already premultiplied, you > could try "oiiotool --no-autopremult in.png -o outputfile.ext" to suppress > the premultiplication that would ordinarily happen when reading PNG files, > then write to a new file. > Sounds like a plan! > But you are right, if you assume that Nuke doesn't know if alpha is > associated or not, and some nodes assumes it's not and some assume that it > is, then the situation can't really be improved other than perhaps a option > on the file writer to make it more obvious. > > That's what I had in mind too, just a checkbox in the Nuke PNG reader/writer to highlight the potential problem. It's not just the oiio reader that premultiplies, Photoshop and other Adobe products does it too. They force premultiply based on how data should be present according to the PNG specification. Thanks all! Mikael
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