PNG and Alpha

[kimgar]

sorry for asking this question again, i realize it's been solved with photoshop's 'remove black matte' a thousand times in this forum,
but my problem is that i have a client that can't be expected to have that kind of knowledge.

i need to render some objects with transparent background so that my client can easily mount them in various settings.
i've tried 'don't antialias against background', 24 bit, 48 bit, white, black, no filters, sub pixels and god knows what,
but i just cant seem to get that straight unmultiplied alpha i thought png's should have:

PNG uses "unassociated" or "non-premultiplied" alpha so that images with separate transparency masks can be stored losslessly.

from www.w3.org about png's, written in 1996, but i guess it still applies...

...any ideas on how to get that straight png alpha into photoshop?

[kimgar]

hmm, of course i could do the 'remove black matte' step in PS, save it again as a png, and voila!

...but still it would be great if someone knew a trick to save a straight png alpha from max

[Dynedain]

Here's what we do:

From Max, render with a black background, save to a 32bit Targa with premultiplied alpha unchecked.

Open that in Photoshop and use Jon Seagull's nifty Targa to PS transparency action


BTW... Photoshop screws up transparencies in general... for PNG it doesn't seperate transparencies to an alpha channel, and never turns alpha into transparency without manually making layer masks.

[kimgar]

thanks for the link dynedain, handy action!

i did a quick test, and the results are pretty much identical to 'remove black matte' from a png:

png on the left, tga on the right:


i'm quite amazed, how photoshop manages to screw up such an important thing as transparencies, it's a shame really

[Dynedain]

i'm quite amazed, how photoshop manages to screw up such an important thing as transparencies, it's a shame really

Yeah, it's very annoying.... every other program that handles alpha channels treats them as transparency, except photoshop. And photoshop transparency doesn't automatically mean alpha channel either.

[kimgar]

f*****g a*s, its' getting late, and i'm really starting to hate adobe - they got me back on track with premiere 2 which actually was quite good, but this alpha issue with PS is just to dumb - can't just tell my clients to start using gimp or irfanview either...bahrhh

[Dynedain]

You could just batch the action to a photoshop "droplet" and send your clients .psd files instead of .png

[kimgar]

droplets sounds like a good plan dynedain, gotta check that out!

it's past midnight already, and our renderfarm just crashed completely, aww...this is too much - i'm going to bed, and i won't wake up until a few weeks have passed, and our 64 bit stations have arrived...