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 Posted: Wed Feb 24, 2016 11:05 pm

Joined: Wed May 19, 2010 6:12 pm
Posts: 2749
I was thinking about colorspaces today, and I came up with a decent idea for a color space that can easily be converted to low-bit rgb, that should be a little more visually uniform than rgb.

I think I'll call it Yab, just because the Y works like the Y in YUV and YIQ, and the A and B work sort've like the A and B in Lab. So here's my formula.

R = Y + 2a + b
G = Y - a
B = Y - 3b

Any advice to improve upon this. I'm thinking there should be a way to compensate for the not-so-predictable luminance value of highly saturated colors.

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 Posted: Wed Feb 24, 2016 11:21 pm

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7519
Location: Seattle
This doesn't really look all that much more useful than RGB?

Here's a simple cube, 0≤Y≤7, -4≤a,b≤3:
Attachment:

yab.png [ 615 Bytes | Viewed 3967 times ]
Lots of out-of-gamut colors too.

No yellows, and lackluster reds and purples.

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 Posted: Wed Feb 24, 2016 11:30 pm

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
Maybe A/B range from 0 to 7, not -4 to 3?

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 Posted: Wed Feb 24, 2016 11:39 pm

Joined: Wed May 19, 2010 6:12 pm
Posts: 2749
Or try -7 to 7. BTW, why is everything so dark?

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 Posted: Thu Feb 25, 2016 10:58 pm

Joined: Fri Nov 19, 2004 7:35 pm
Posts: 4076
Sounds very similar to YCgCo, but not quite the same.

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 Posted: Fri Feb 26, 2016 10:29 am

Joined: Wed May 19, 2010 6:12 pm
Posts: 2749
Dwedit wrote:
Sounds very similar to YCgCo, but not quite the same.

I never heard of that before, but it sounds awesome.

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 Posted: Fri Feb 26, 2016 6:33 pm

Joined: Wed May 19, 2010 6:12 pm
Posts: 2749
I made a 12-bit YCoCg color palette. It's cool how it ended up being exactly 1024 colors. That means if I make a 15-bit version, it will come out with 8192 colors.

 Attachments: YCoCg.png [ 2.55 KiB | Viewed 3825 times ]
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 Posted: Fri Feb 26, 2016 8:09 pm
 Formerly Espozo

Joined: Mon Sep 15, 2014 4:35 pm
Posts: 3362
Location: Richmond, Virginia
I always wondered how having 6bit RGB with 2 extra bits to reduce the value of the color for every channel. Because your eyes are supposedly better at seeing shades of color than different colors or something like that, I wonder if it might even look better than 9bit RGB despite only being half the colors.

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 Posted: Fri Feb 26, 2016 8:46 pm

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 20556
Location: NE Indiana, USA (NTSC)
That's a form of RGBI, with 2 bits per channel. It's the componentwise sum of the Cartesian product of four 2-bit palettes:

Red: #000, #400, #800, #C00
Green: #000, #040, #080, #0C0
Blue: #000, #004, #008, #00C
Intensity: #000, #111, #222, #333

Fortunately, GIMP makes componentwise sums easy using the Addition blend mode.

 Attachments: File comment: The four subpalettes layers.png [ 738 Bytes | Viewed 3801 times ] File comment: The palette added.png [ 1.42 KiB | Viewed 3801 times ] File comment: Parrot in RGBI2222. Left: not dithered; right: Floyd-Steinberg dithered. parrot.png [ 31.01 KiB | Viewed 3801 times ]
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 Posted: Sat Feb 27, 2016 6:01 am

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
May as well compare it against my colorspace:

RGB 3.3.3, but red and blue share the LSB (so it fits in 8-bit). I came up with it because I honestly hate how little resolution blue has in RGB 3.3.2, which wouldn't be much of an issue except because it seems new "retro" hardware insists on using that (argh!).

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 Posted: Sat Feb 27, 2016 8:08 am
 Formerly Espozo

Joined: Mon Sep 15, 2014 4:35 pm
Posts: 3362
Location: Richmond, Virginia
I thought I'd try seeing how Sik's palette looks:

Attachment:

Sik's Palette.png [ 13.58 KiB | Viewed 3746 times ]

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 Posted: Sat Feb 27, 2016 11:42 am

Joined: Mon Feb 07, 2011 12:46 pm
Posts: 1013
I thought of a different kind of colorspace: 3-bits high-voltage, 3-bits low-voltage, 3-bits phase. The phase only covers half, because you can get the rest of the phases by inverting it which is done by switching the voltage. If high-voltage and low-voltage is same then the picture will be gray.

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 Posted: Sat Feb 27, 2016 11:52 am

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7519
Location: Seattle
Espozo wrote:
I always wondered how having 6bit RGB with 2 extra bits to reduce the value of the color for every channel.
tepples wrote:
It's the componentwise sum of the Cartesian product of four 2-bit palettes:
I assumed that Espozo meant something with a multiplier, not RGBI.

Here's the equivalent palette where I parse the last two bits as a all-channels multiplier that ranges from 1 to 4:
Attachment:

rgbmult.png [ 1.24 KiB | Viewed 3713 times ]

It's really lacking in pastels, though, so the parrot doesn't look so good:
Attachment:
File comment: left: plain
right: floyd-steinberg dithering

rgbmultparrot.png [ 29.77 KiB | Viewed 3713 times ]

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 Posted: Sat Feb 27, 2016 11:56 am

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
Actually his description sounds more like reverse RGBI, where I substracts instead of adding (you could achieve that just by passing I through a NOT). But yeah it's not very clear honestly.

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 Posted: Sat Feb 27, 2016 12:16 pm
 Formerly Espozo

Joined: Mon Sep 15, 2014 4:35 pm
Posts: 3362
Location: Richmond, Virginia
Yeah, I didn't mean multiplying. I meant what Sik is talking about. I'm not sure how different than would look than tepples's though.

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