"ingo" <nomail@nomail> wrote:

> The problem is I don't understand the problem,

So, it looks to me to be like this:

When POV-Ray uses an assumed_gamma that is <> 1, it funnels everything through a
function that translates all of the colors from a line to a curve.

Also, when images are encoded using a gamma <> 1, the same thing happens.

So if you're going to use byte-encoded (s)rgb values from a color picker, then
you're not going to be funneling them through any kind of software that "reads
the image in" - you're manually bypassing that.  So you wind up having to
manually do the correction yourself with the srgb keyword to pull all of the
colors back into the linear space _of the pre-rendered SDL file_ before then
rendering your image with what may be a(nother) non-linear gamma <>1.
So if you just used the byte-encoded color values, you'd wind up applying gamma
adjustments twice - the one that is inherent in the sampled image color values,
and then the one that POV-Ray applies when you render the image with a gamma <>
1.

Now, anyone familiar with film gamma knows that higher gamma values give you a
more "contrasty" look than a gamma=1 image.   So think about what happens when
you think you're using srgb values, but you're using rgb values, and then
correct for a higher gamma to translate that into linear space --- you bend that
gamma curve in the _opposite_ direction - giving rise to that "washed out" look,
because you've _decreased_ the contrast of the color space.

SO, I think what we may want to see are several things.
An RGB cube viewed from a corner to give that nice RGB hexagon.
(I think that having a function {} using hexagonal coordinates to just color a
hexagonal prism would be nice little tool.)
A single image rendered as strips of increasing gamma, to show the differences.
Color strips and graphs to show the change in hue and brightness.
Do we have a mathematical way to express "gamma" or "contrast", given the full
range of color values in an image?


It's early, and the coffee is still sinking in, so I don't fully understand why
gamma gets applied to an image in the first place - unless it's just a way to
preserve the original gamma=1 color values for image-editing purposes.

- BW

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