Learned friends, I have been working on a scene for what seems like all my
life, and have always viewed the resulting PNGs in POV's previewer, qiv,
ImageMagick's display, the Gimp, and Eye of Gnome.  All of these display my
scene as I expect.

To my dismay, my PNGs are far too bright in Firefox, Mozilla, and IE.

ImageMagick says the gamma in my PNGs is 1.0, no matter what I set my
assumed_gamma setting.  When I use the same POV binary to render the POV
example scenes, such as  biscuit.png and benchmark.png, the gamma in the
output PNG is 0.45455 (1/2.2).

biscuit.png and benchmark.png look the same all applications.  I use the
official 3.6.1 binary.

I'm clearly doing something wrong.  The gamma in output PNGs should change
with assumed_gamma, no?  Someone please slap me, because if this carries on
I shall have to switch to JPEG.

Many, many thanks in advance.

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Ard <ard### [at] waikatoacnz> wrote:
> I'm clearly doing something wrong.  The gamma in output PNGs should change
> with assumed_gamma, no?  Someone please slap me, because if this carries on
> I shall have to switch to JPEG.

  I don't know about the problem per se, but you can use eg. the Gimp to
remove the gamma value from a PNG file.

-- 
                                                          - Warp

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In article <43744f7e@news.povray.org>, war### [at] tagpovrayorg says...
> Ard <ard### [at] waikatoacnz> wrote:
> > I'm clearly doing something wrong.  The gamma in output PNGs should change
> > with assumed_gamma, no?  Someone please slap me, because if this carries on
> > I shall have to switch to JPEG.
> 
>   I don't know about the problem per se, but you can use eg. the Gimp to
> remove the gamma value from a PNG file.
> 
My bet, he has it set to 2.2, because that is what he is assuming his 
display is, but the programs he is viewing it in 'think' his display is 
1.0, so they are 'correctly' adjusting the image to match what they 
believe won't be displayed correctly on they hardware they are running on 
(which they assume is a gamma of 1.0).

-- 
void main () {

    call functional_code()
  else
    call crash_windows();
}

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> My bet, he has it set to 2.2, because that is what he is assuming his
> display is, but the programs he is viewing it in 'think' his display is
> 1.0

That would account for it too, but it turned out to be a bug in POV.  Line
594 in png_pov.cpp sets the gamma value in PNGs to 1.0 when the user
requests a CPU histogram.

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Ard wrote:
>>My bet, he has it set to 2.2, because that is what he is assuming his
>>display is, but the programs he is viewing it in 'think' his display is
>>1.0
> 
> That would account for it too, but it turned out to be a bug in POV.  Line
> 594 in png_pov.cpp sets the gamma value in PNGs to 1.0 when the user
> requests a CPU histogram.

Of course, the histogram is only going to be meaningful if it is not gamma 
corrected.  Hence the value is set to 1, which implies no gamma correct.

	Thorsten

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Thorsten Froehlich <tho### [at] trfde> wrote:

> Of course, the histogram is only going to be meaningful if it is not gamma
> corrected.  Hence the value is set to 1, which implies no gamma correct.

Setting the gamma to 1 makes sense for the CPU histogram, but it should not
set the gamma to 1 when it is writing the *scene* image file.

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