"Bald Eagle" <cre### [at] netscapenet> wrote:
> So, I may be way off base here, but I just wanted to speculate, to promote
> clarification of what's going on.
>
> It occurred to me that what Kenneth might be seeing is an artifact of one gamma
> "stretching" the color values sufficiently so that they skip over some of them.
> I now also wonder if he's missing a "compression" in another part of the
> mapping, where one value gets represented twice, and so it _looks_ like a single
> instance.
>
> Probably something to do numerically rather than graphically to really see
> what's going on.
>
> Just some thoughts.

One thing you might try is, rather than use png, use gif.

https://en.wikipedia.org/wiki/GIF

It seems that gif exclusively used an indexed color palette (color look up
table).

Then you can simply open the gif in IrfanView, and use Image > Information, and
it will tell you how many unique color indices you have.

If you're going to do graphic / visual experiments, it might be worth assembling
a color_map such that your color entries are non-adjacent in the color wheel.
So, all of the even entries would be "monotonically" increasing from 0, and all
the odd entries would get shifted - say, by adding 127, and taking mod(N, 255)
to get the result that's "wrapped around to 0".
That way, you get maximum contrast between color indexes, and might be better
able to see doubled entries.
You'd need hard stops in your color map to prevent interpolation between
entries, and then you could simply render a smooth gradient across a wide image
format (1920 x 1080).

- BW

Post a reply to this message