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PNG image becomes too bright
Posted: 2015-03-02T23:53:21-07:00
by oleksiy
An sRGB PNG image becomes too bright even with no processing options specified:
test.png:
https://www.dropbox.com/s/6ia85553der2lwu/test.png?dl=0
test2.png:
https://www.dropbox.com/s/mexp6kl69msiw ... 2.png?dl=0
ImageMagick 6.9.0-3 Q16 x86_64
Thanks!
Re: PNG image becomes too bright
Posted: 2015-03-03T00:07:09-07:00
by snibgo
The images seem identical.
test.png has a gamma setting of 2.2, which is very high. More usual numbers would be 0.454545 (which is 1/2.2, for sRGB) or 1.0 (for linear RGB).
Code: Select all
convert test.png -set gamma 0.454545 t.png
Re: PNG image becomes too bright
Posted: 2015-03-04T23:11:44-07:00
by oleksiy
Yes, thats strange, probably Dropbox shows modified images and it corrects the problem. Please download them as original from Dropbox (with right click) and you'll see the difference.
Here is a screenshot of how the second image looks after 'convert':
https://www.dropbox.com/s/6ynfkwqhn2k8d ... 3.png?dl=0
Re: PNG image becomes too bright
Posted: 2015-03-05T00:02:55-07:00
by snibgo
I did download as you say.
What software made test.png? Why does it have gamma=2.2 instead of the more usual 1/2.2? Some software will ignore this setting and assume it is really 1/2.2. Other software, like Firefox and ImageMagick, will use this setting and so it appears bright.
The cure is to put the proper setting into test.png.
