It is currently Sun Oct 22, 2017 5:58 pm

All times are UTC - 7 hours





Post new topic Reply to topic  [ 31 posts ]  Go to page Previous  1, 2, 3  Next
Author Message
PostPosted: Sat Feb 27, 2016 1:26 pm 
Offline

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 19115
Location: NE Indiana, USA (NTSC)
zzo38 wrote:
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.

That'd be HSL-ish, sort of like NES except including more desaturated midtones. It'd be simple to implement a composite output circuit for (assuming an 8*CB crystal), but I can't so easily show the parrot for this one because it has 8*8*8-8*7 = 456 colors, and GIMP won't quantize to palettes with more than 256 colors.

Sik's suggestion to subtract the intensity instead of adding it would be mathematically equivalent to the purely additive RGBI if defined as follows:

Red: #300, #700, #B00, #F00
Green (add): #030, #070, #0B0, #0F0
Blue (add): #003, #007, #00B, #00F
Intensity (subtract): #333, #222, #111, #000


Top
 Profile  
 
PostPosted: Sat Feb 27, 2016 4:37 pm 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
Really the only difference is that the order of the colors has changed, but the available colors are pretty much the same. May as well just go with additive at that point and make everybody's lives easier.

Somebody should go and glue two EGAs together...


Top
 Profile  
 
PostPosted: Sun Feb 28, 2016 6:09 pm 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
Something I remembered: I know some LCDs work by shifting hues instead of shifting luminance. What about a colorspace where you layer both kind of LCDs on top of each other? Would it have been a reliable way to get color on early handhelds without eating battery like hell? Biggest problem (aside from the obvious blurring) is that saturation would be always at max. Still, would be a fun experiment to think about.


Top
 Profile  
 
PostPosted: Sun Feb 28, 2016 6:55 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6297
Location: Seattle
So-called "Electronically Controlled Birefringence" Displays are achievable (scroll down to "COF LCD module"). They have a rather peculiar color palette, though.

There was a Pokemon-themed pedometer that used it. (video)


Top
 Profile  
 
PostPosted: Sun Feb 28, 2016 8:08 pm 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
So wait, their range can be stretched to do more than just a hue shift? Because that actually seems more useful. (my original idea was to use that for hue and then another display on top that was monochrome for luminance)


Top
 Profile  
 
PostPosted: Tue Mar 01, 2016 2:45 am 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
Here's another idea: HSL 4.2.2

  • When bits 7-4 are 0000, the color is grayscale and bits 3-0 are the luminance.
  • Otherwise, bits 7-4 specify hue (in steps of 24º), bits 3-2 the saturation (25%,50%,75%,100%) and bits 1-0 the luminance (20%,40%,60%,80%).

EDIT: fixed my HSL algorithm and ditched the old image

Image

Still leaves a lot to be desired.


Top
 Profile  
 
PostPosted: Tue Mar 01, 2016 8:16 am 
Offline
User avatar

Joined: Sat Feb 12, 2005 9:43 pm
Posts: 10066
Location: Rio de Janeiro - Brazil
Sik wrote:
Image

I like the colors, but fading in this color space looks complicated, especially since grays are treated differently.


Top
 Profile  
 
PostPosted: Tue Mar 01, 2016 1:21 pm 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
I think that fading is hell with most of the colorspaces mentioned here though =P Would make for a good default 256 colors palette though.

I'm not happy with how coarse luminance turns out to be, though =/


Top
 Profile  
 
PostPosted: Tue Mar 01, 2016 6:24 pm 
Offline

Joined: Thu Aug 20, 2015 3:09 am
Posts: 284
Why does the highest luminance level also lower saturation? Saturation increases perceptual brightness, so that seems counterproductive, not to mention redundant.


Top
 Profile  
 
PostPosted: Tue Mar 01, 2016 11:24 pm 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
That's how HSL works, maybe you were thinking on HSV instead?


Top
 Profile  
 
PostPosted: Wed Mar 02, 2016 7:14 pm 
Offline

Joined: Thu Aug 20, 2015 3:09 am
Posts: 284
I was thinking purely in terms of getting the most usable colors out of the palette. Now that you mention it though, HSV is probably what I was suggesting.


Top
 Profile  
 
PostPosted: Wed Mar 02, 2016 9:37 pm 
Offline

Joined: Thu Aug 12, 2010 3:43 am
Posts: 1589
OK giving a try to HSV (same format otherwise), assuming I got the calculation right (was expecting this to be harder):

Image


Top
 Profile  
 
PostPosted: Wed Mar 02, 2016 10:23 pm 
Offline
User avatar

Joined: Sat Feb 12, 2005 9:43 pm
Posts: 10066
Location: Rio de Janeiro - Brazil
So, in order to fade to black you'd alternate between decreasing V and increasing S, and to fade to white you'd alternate between decreasing S and increasing V?


Top
 Profile  
 
PostPosted: Sun Mar 27, 2016 12:10 am 
Offline
Formerly 43110
User avatar

Joined: Wed Feb 05, 2014 7:01 am
Posts: 311
Location: us-east
Last time I tried making an 8-bit color space with a good luminance range I ended up with this quite arbitrary palette:

Image

I found that the RGBI palette that tepples posted earlier could be rearranged to emphasize grayscales but still have all the same colors.

Attachment:
2016-03-27_2bit-BRGI.png
2016-03-27_2bit-BRGI.png [ 948 Bytes | Viewed 1020 times ]

Code:
Index: bbrrgggg
R = gggg + rr00
G = gggg
B = gggg + bb00

This would be the palette I would use if I was designing another Uzebox or something. Maybe replace the additions with XORs to simplify circuit design.


Top
 Profile  
 
PostPosted: Sun Mar 27, 2016 9:02 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6297
Location: Seattle
JRoatch wrote:
Index: bbrrgggg
R = gggg + rr00
G = gggg
B = gggg + bb00
If the digital values are just converted linearly there's no greens at all:
Attachment:
bbrrgggg_addition.png
bbrrgggg_addition.png [ 1.24 KiB | Viewed 983 times ]

If you normalize green so it's the same range (i.e. scale up from 0-15 up to R and B's 0-27), it's ... ok?
Attachment:
bbrrgggg_addition_normalized.png
bbrrgggg_addition_normalized.png [ 1.32 KiB | Viewed 983 times ]

Quote:
replace the additions with XORs

That produces an interesting set of colors:
Attachment:
bbrrgggg_xor.png
bbrrgggg_xor.png [ 1.35 KiB | Viewed 983 times ]


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 31 posts ]  Go to page Previous  1, 2, 3  Next

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group