There's definitely something going wrong on the oiiotool side... in particular, the -iconfig oiio:UnassociatedAlpha 1 is getting lost somehow.
> On Feb 8, 2019, at 3:15 PM, Stephen Parker <[email protected]> wrote: > > re: unassociated alpha - I ran into something similar when pushing PNG's to > iOS devices from XCode. Apparently Apple uses a modified libpng and added a > special chunk denoting that the file (against the png spec) is premultiplied > and XCode did that premult step automagically when bundling. That took awhile > to figure out. This test.png is NOT one of those files though. It comes from > Unity. Thanks again for digging into it. > > > On Fri, Feb 8, 2019 at 3:02 PM Larry Gritz <[email protected] > <mailto:[email protected]>> wrote: > I can answer that question, but then it leads right back to something ELSE > that's probably my fault. :-) > > OK, so PNG is, by specification, "unassociated alpha" (what some people call > "un-premultiplied"), and OIIO by convention always passes <ahem, CORRECT> > "associated alpha", which means that when reading unassoc files it will > automatically multiply RGB by A before giving the values to the app. > > Your file has alpha = 0, which is supposed to mean (for PNG) that the > appearance is black everywhere. > > This auto-conversion of unassociated to associated that happens in OIIO's PNG > reader can be disabled with a special configuration attribute, so the correct > command line should have been this: > > oiiotool -iconfig oiio:UnassociatedAlpha 1 steveparker.png -ch R,G=R,B=R,A=R > -o out.tif > > ... Except something is going wrong there as well. Ugh. I'm trying to > understand why. Stand by. > > > >> On Feb 8, 2019, at 2:52 PM, Stephen Parker <[email protected] >> <mailto:[email protected]>> wrote: >> >> Indeed. That was my first reaction too. But then why doesn't this work: >> >> oiiotool test.png --ch "R=R,B=R,G=R" -o out.png >> >> oiiotool test.png --ch "R=R,B=R,G=R,A=1.0" -o out.png >> >> I figured it was user error. >> >> >> >> >> On Fri, Feb 8, 2019 at 2:39 PM Larry Gritz <[email protected] >> <mailto:[email protected]>> wrote: >> Doesn't the fact that everything interesting ends up in out-0.png tell us >> that the alpha was black all along, and it was the red channel that you're >> after? >> >> >>> On Feb 8, 2019, at 2:03 PM, Stephen Parker <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> ... actually, disregard the -swap as -separate is all that's needed. >>> >>> convert test.png -separate out.png >>> >>> On Fri, Feb 8, 2019 at 1:51 PM Stephen Parker <[email protected] >>> <mailto:[email protected]>> wrote: >>> Try: >>> >>> convert test.png -separate -swap 4,0 out.png >>> >>> You should get an image written out for each channel. "out-0.png" can be >>> opened in Preview.app. >>> >>> -s >>> >>> >>> On Fri, Feb 8, 2019 at 1:38 PM Larry Gritz <[email protected] >>> <mailto:[email protected]>> wrote: >>> On my mac, ImageMagick "convert test.png test.tif" also results in what >>> appears to be a black image. >>> >>> And using ImageMagick's "identify -verbose", I see these stats: >>> >>> Alpha: >>> min: 0 (0) >>> max: 0 (0) >>> mean: 0 (0) >>> standard deviation: 0 (0) >>> kurtosis: -3 >>> skewness: 0 >>> entropy: 0 >>> >>> Are you *sure* that the alpha channel isn't really 0 everywhere? >>> >>> >>> >>>> On Feb 8, 2019, at 11:55 AM, Larry Gritz <[email protected] >>>> <mailto:[email protected]>> wrote: >>>> >>>> Hmmm... it's not just "--ch", that image looks "black" (all 0.0 values) in >>>> all channels to all OIIO tools. (For example, `oiiotool -stats test.png`) >>>> I'm suspecting something in the reader rather than an issue with channel >>>> selection. >>>> >>>> Looking into it. >>>> >>>> -- lg >>>> >>>> >>>>> On Feb 8, 2019, at 11:31 AM, Stephen Parker <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>> >>>>> Hi Larry, >>>>> >>>>> I'm on the release branch. Here is the PNG in question (attached). >>>>> >>>>> thanks >>>>> >>>>> On Fri, Feb 8, 2019 at 11:12 AM Larry Gritz <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>> Which version of OIIO? >>>>> And I don't suppose you can send me an example PNG that has the problem? >>>>> Or is it weird for every png you try? >>>>> >>>>> >>>>> >>>>>> On Feb 8, 2019, at 10:59 AM, Stephen Parker <[email protected] >>>>>> <mailto:[email protected]>> wrote: >>>>>> >>>>>> Hello, >>>>>> >>>>>> I'm having some trouble using oiiotool's copy channel operator. It might >>>>>> be user error but I wanted to check and see if it's intended behavior. >>>>>> I've only glanced at the code so far. >>>>>> >>>>>> My test image is a PNG (4-channel RGBA), but only has information in the >>>>>> Alpha. When attempting to copy the Alpha into the other 3 channels and >>>>>> write out an RGB image (no Alpha), I get black. Imagemagick's 'convert' >>>>>> did what I expected. >>>>>> >>>>>> invoked as: >>>>>> >>>>>> oiiotool input.png --ch "R=A,G=A,B=A" -o output.png >>>>>> >>>>>> I also tried using the numeric channel labels to no avail. >>>>>> >>>>>> -sp >>>>>> _______________________________________________ >>>>>> Oiio-dev mailing list >>>>>> [email protected] <mailto:[email protected]> >>>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >>>>> >>>>> -- >>>>> Larry Gritz >>>>> [email protected] <mailto:[email protected]> >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Oiio-dev mailing list >>>>> [email protected] <mailto:[email protected]> >>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >>>>> <test.png>_______________________________________________ >>>>> Oiio-dev mailing list >>>>> [email protected] <mailto:[email protected]> >>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >>>> >>>> -- >>>> Larry Gritz >>>> [email protected] <mailto:[email protected]> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> Oiio-dev mailing list >>>> [email protected] <mailto:[email protected]> >>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >>> >>> -- >>> Larry Gritz >>> [email protected] <mailto:[email protected]> >>> >>> >>> >>> >>> _______________________________________________ >>> Oiio-dev mailing list >>> [email protected] <mailto:[email protected]> >>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >>> _______________________________________________ >>> Oiio-dev mailing list >>> [email protected] <mailto:[email protected]> >>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >> >> -- >> Larry Gritz >> [email protected] <mailto:[email protected]> >> >> >> >> >> _______________________________________________ >> Oiio-dev mailing list >> [email protected] <mailto:[email protected]> >> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> >> _______________________________________________ >> Oiio-dev mailing list >> [email protected] <mailto:[email protected]> >> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> > > -- > Larry Gritz > [email protected] <mailto:[email protected]> > > > > > _______________________________________________ > Oiio-dev mailing list > [email protected] <mailto:[email protected]> > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org> > _______________________________________________ > Oiio-dev mailing list > [email protected] > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org -- Larry Gritz [email protected]
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