Re: 24-bit-per-pixel limit to Gdk RGB ?

On Tue, 18 Feb 2003, Thomas Cameron wrote:

Roland Smith wrote:

On Tue, 18 Feb 2003 17:16:33 -0300
individual <individual mi cl> wrote:


That's interesting. I was always under the imprsesion that we have left 
24bpp displays far behind. Here's what my system says:

Resolution        Video Memory

640 x 480               32-bit
800 x 600             32-bit
1024 x 768          32-bit

I _think_ that those 8 extra bits are for alpha blending (transparency). 


Eek.... I was hoping for greater bit depth, but I'm getting more and 
more convinced that it's pointless to try and render a 48 bpp image at 
48 bpp screen depth when screens are at most 24bpp deep.

It's not pointless. You won't lose much quality. Consider: on a 1024*768 monitor
you can only display 786432 different colors (if every pixel has a different
color, which is quite rare, unless you've got some very psychedelic images)

To be able to display all the colors in an 24bpp gamut, you'll need 16777216
((2^8)^3) pixels, which is something like 4729*3547 in traditional 4:3 ratio. If
you come across a cheap display that can handle this, let me know. :-)


The format is this:

32 bit display: 8-bits RED, 8-bits GREEN, 8-bits BLUE, 8-bits ALPHA
16 bit display: 8-bits RED, 8-bits GREEN, 8-bits BLUE

8+8+8=24 not 16. When they are coded with 16 bits, there is 65536 colors 
(2^16). I have read that, in that case (16 bit display) , red and blue was 
both coded with 5 bits and green with 6 bits. It surprised me and I don't 
know at all if this is the case (if there is an additional bit for the 
green color). If someone has a comment...

This is for computer monitor displays, of course.  Personally, I have 
never heard of a 48bpp display, and I am quite certain that the human 
eye could not distinguish such a small degree of difference.  Of course, 
if you are a quality-phile, like me, you would render in 48bpp anyway.  ;-)

The eye can distinguish 2000000 of colors, a display of 24 bits gives a 
number of colors far beyond what we can see.

Vincent TORRI

Good luck,
Tom Cameron

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TORRI Vincent
Mathematiques Appliquees Bordeaux                                                
Institut de Mathematiques                                                       
Universite Bordeaux 1                                                           
351 cours de la liberation                                                      
33 405 Talence cedex - France                                                   
Tel : 33 (0)5 57 96 21 42                                                       
Fax : 33 (0)5 56 84 26 26                                                       

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