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Re: true color executor/D



In article <4e5gg2$f6@newsstand.cit.cornell.edu>,
William Magro <wmagro@msc.cornell.edu> wrote:
>Scott Shuchart (shuchart@fas.harvard.edu) wrote:
>
>: This situation doesn't make sense to me.  640x480x256 is 1Mb Vram, no matter 
>: what the colors are.  And grays are just some colors.  [...]
>
>The catch here is that the 256 colors of VGA are chosen from a palette
>of 256k (or fewer) colors with standard VGA cards.  Since each gray
>must have equal components of red, green, and blue, this reduces the
>effective number of true grays to 64 [=262144^(1/3)].  It takes a
>24-bit D/A converter (8-bits in each channel) to generate 256 grays.
>
>In the end, the number of grays you can generate depends on the bitness
>of your DAC and the smarts of the video driver.

But most all cards capable of doing more than 256 colors also have 24-bit (as
opposed to 18-bit) DACs.  My s3-968 based card can do 256 greyscales when in
8-bit pseudocolor mode.  So can just about any modern graphics card.

-- 
|Gazing up to the breeze of the heavens \ on a quest, meaning, reason  |
|came to be, how it begun \ all alone in the family of the sun         |
|curiosity teasing everyone \ on our home, third stone from the sun.   |
|Trent Piepho (xyzzy@u.washington.edu)                   -- Metallica  |


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