Fredrik Eriksson <fe79}--at--{yahoo}--dot--{com> wrote:
> On Thu, 03 Sep 2009 18:02:46 +0200, Warp <war### [at] tagpovrayorg> wrote:
> >   Saying that v3.6 did it wrong is not very helpful for someone who is
> > trying to render a 3.6 scene using POV-Ray 3.7.

> One could argue that using "#version 3.6" should completely mimic the  
> behaviour of v.3.6, but that does not mean v3.7 should behave the same by  
> default.

  I agree, but my point is that at least the current 3.7 beta doesn't fully
emulate 3.6 in the way it creates the PNG file. (It does work when rendering
to other image formats.)

> The whole point of using a gamma-aware image format is that you do not  
> need to counter the gamma correction; it is handled correctly by default.  
> The problems arise only when using gamma-unaware formats.

  It can be a problem if rgb 0.5 does not write (127,127,127) to the file
but something else. The problem is that if you really need a linear
relationship between colors and pixel values, doing any kind of gamma
transformation is going to destroy some of that information.

  In other words, if you were creating a linear gradient from left to right
on a 256-pixel wide image, what you want is

    (0,0,0)(1,1,1)(2,2,2)(3,3,3)(4,4,4)(5,5,5)...(255,255,255)

to be written to the file. What you *don't* want is that after a gamma
correction and uncorrection process you end up having something like

    (0,0,0)(2,2,2)(2,2,2)(3,3,3)(5,5,5)(5,5,5)...(255,255,255)

-- 
                                                          - Warp

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