I confirmed the patch works on my end. And sorry about the initial misinformation regarding the particular channel. I had tried it so many different ways I think I confused myself. One would assume if you wrote a 4-channel image there would be some information in that channel or at least all 1.0's. Anyway, at least we got a bug out of it. Thank you for tracking that down so quick!
On Sat, Feb 9, 2019 at 4:36 PM Larry Gritz <[email protected]> wrote: > Aha! This was a little tricky to find, but here is the fix: > > https://github.com/OpenImageIO/oiio/pull/2172 > > I believe that with this fix in place, the following command ought to work > with your file: > > oiiotool -iconfig oiio:UnassociatedAlpha 1 steveparker.png -ch > R,G=R,B=R,A=R -o out.tif > > > On Feb 8, 2019, at 3:18 PM, Larry Gritz <[email protected]> wrote: > > 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]> 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]> >> 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]> 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]> >>> 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]> 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]> 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]> 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]> 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]> 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]> 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] >>>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>>> >>>>>> >>>>>> -- >>>>>> Larry Gritz >>>>>> [email protected] >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> Oiio-dev mailing list >>>>>> [email protected] >>>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>>> >>>>> <test.png>_______________________________________________ >>>>> Oiio-dev mailing list >>>>> [email protected] >>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>> >>>>> >>>>> -- >>>>> Larry Gritz >>>>> [email protected] >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Oiio-dev mailing list >>>>> [email protected] >>>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >>>>> >>>>> >>>>> -- >>>>> Larry Gritz >>>>> [email protected] >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Oiio-dev mailing list >>>>> [email protected] >>>>> 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] >>> >>> >>> >>> >>> _______________________________________________ >>> Oiio-dev mailing list >>> [email protected] >>> 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] >> >> >> >> >> _______________________________________________ >> Oiio-dev mailing list >> [email protected] >> 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] > > > > > _______________________________________________ > Oiio-dev mailing list > [email protected] > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > > > -- > Larry Gritz > [email protected] > > > > > _______________________________________________ > Oiio-dev mailing list > [email protected] > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >
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