clipka <ano### [at] anonymousorg> wrote:
> Am 05.08.2017 um 04:12 schrieb Kenneth:
> > I just noticed something strange about the PNG images I posted: When I look at
> > the small *preview* images here in my post (using the latest version of
> > Firefox), they look correct...
> > But when I click on the image previews here-- and the higher-resolution
> > versions appear-- the gamma of the images isn't correct! They look
> > darker, with more contrast.

>
> My bet is that you instead have a wonky post-processing workflow, as
> your PNG file is seriously odd: The `gAMA` chunk in your PNG file claims
> that the file was encoded with a gamma of 0.22727 = 1/4.4 (or
> "pre-corrected for a display gamma of 4.4", as it would be called in
> other file formats), rather than the typical 0.45455 = 1/2.2; I suspect
> that `gAMA` chunk is outright wrong.

Agreed, without reservation ;-) I have no clue as to why my (older v5.0) of
Photoshop would create such an *extremely* wrong gamma encoding. I knew it was
somewhat wonky (from reading about its possible PNG problems years ago)--but not
to that degree!
>
>
> For the JPEG file format, as far as gamma goes there's only a W3C
> recommendation for use on the internet. The file format itself is
> blissfully unaware of gamma. So you just have to pray that the target
> system /happens/ to interpret them in the way you intended them to be
> interpreted.

I assumed that just about all relatively recent flat-panel monitors are
factory-preset gamma-wise to show JPEGs correctly. I guess that has always been
my own rather dubious 'benchmark' for using JPEG vs. PNG. (And I'm coming to
realize that my own doubts about PNG actually owe their origin to my crappy
version of Photoshop! I've been using it WAY past its 'expiration date'. But the
'pain' of dealing with PNGs there is hard to forget.)

I now understand the newsgroup 'problem' I encountered with my
originally-uploaded Photoshop'd PNG file--that crazy gamma 4.4 image: The
'small' preview in the newsgroup is modified (for want of a better term) to look
'correct' no matter what it's gamma might be (or when there's no intrinsic gamma
at all, in the case of JPEGs); whereas the 'larger' preview (the much darker
one, in my case) shows the ACTUAL/awful gamma encoding of my image. And I was
assuming the opposite!

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