--- Expanding the C64 palette to 32 colors ---

[yrizoud]

Here's the result of calculation, reordering the colors according to this formula:

[Ai]

Yeah, that formula performs fairly well;It's not quite right, though.
In particular, colors #1 and #2 are swapped, in terms of brightness, as are #3 and #4, #7 and #8

Here are the brightnesses, sRGB intensities calculated via LAB colorspace (using GMIC_gimp custom command "-srgb2rgb -rgb2lab -sh 1,2 -*[-1] 0 -rm[-1] -lab2rgb -rgb2srgb -round"):

0 69 68 86 84 102 105 126 128 137 153 171 180 212 217 255

(this doesn't pick up on the problem with #7 and #8)

And a version calculated via YCbCr: ("-srgb2rgb -to_rgb -rgb2ycbcr -channels 0 -rgb2srgb -round")
(This 'feels' a bit more accurate to my eye)

0[clipped] 96 100 111 105 126 122 141 137 149 150 172 176 204 205

(here the problem with #7 and #8 is picked up, but not the one with #1 and #2.  )

All of them pick up on some errors, but I haven't seen an implementation of any colorspace that's fully perceptually-correct yet.

I began trying linearized RGB with DB's coefficients, but haven't got GMIC to cooperate yet.

[Mathias]

Wow you guys! Some serious math goin' on there . . . uhm so let me see if I understand what's being done - you're taking RGB values and calculating the correct greyscale value from them?
Does the math really matter, though? A palette is such a visual thing. Does it matter if it's mathematically sound? It has to look right to the eye. And even that is subjective. Don't get me wrong, I highly appreciate the math figures being thrown around. Greyscale conversion is the ONE thing, in my workflow, that I HAVE to use ProMotion for. Photoshop doesn't do it right. I don't know of any other software that greyscale converts a color correctly.

I was going off of this at first, to make an even ramp, which I ditched - 100 / 32 = 3.125  -OR-  255 / 32 = 7.968. 32 equal lightness steps.


I've decided to ditch lumapairs and just go with a 32 step luma ramp for the palette - here's the ramp I've worked out:



It doesn't alter the original colors much at all, while lightening up the dark end, creating a larger midtone range in the palette.

I plan to soon to fill in the missing colors. One idea I have for that is to attempt to represent each main RGB spectrum component (Red, Green & Blue) every 3-6 shades. Secondaries and even tertiaries will hopefully make a sufficient appearance. No idea yet . . . we'll see. Might get some time to work on this tonight.

If you feel like taking a crack at inputting some new colors into the future pal, by all mean go for it; would love to have another's palette attempt to bounce my own off of.

[yrizoud]

After his successful search for a 16-color palette, Arne had a try at a 32/64-color one. It may be interesting to watch the process.

[Helm]

Straight up, your two darkest and your two brightest are interchangable, too close they're wasted. Unless you plan to use some supersaturation on them, they won't read as different colors to pure black and pure white.

[Mathias]

After his successful search for a 16-color palette, Arne had a try at a 32/64-color one. It may be interesting to watch the process.

Bugger! I forgot he started a generic 32 color palette project. I'll read that thread thoroughly. Why did it halt I wonder. Thanks, yrizoud.

Helm, you're right. The extreme ends of my little gamma ramp are unsurprisingly troublesome. Monitor profiles can even come into play. I'll certainly pay attention to darkest and lightest colors as I proceed.




*EDIT

[Mathias]

I'd say my palette isn't too bad at the moment. Though I haven't really used it yet. Here it is, in version 3.






Hard to judge a palette without work made with it. Will have to remedy this soon . . .

[HughSpectrum]

I personally can't tell the difference between colors 1 & 2.  5 & 6 are also very similar despite being very different hues.

[Mathias]

Important feedback. Thanks. Not sure how to levy gamma issues across displays. Every display is different. Calibrations, etc. Perhaps I should just lighten the dark end some more.

[ptoing]

If you can not tell the difference between colours 1 and 2 your monitor is set too dark I am afraid.

Colours 5 and 6 however are very, very close in perceptual brightness, which does not mean that they are not helpful tho. Would have to be tested I would reckon.