Re: Digitizing in color??

[foegelle@ccwf.cc.utexas.edu (Michael Foegelle)]

In article <6T1ZTB2w165w@ersys.edmonton.ab.ca> herbertf@ersys.edmonton.ab.ca (Herbert Fung) writes:
>When I worked at Egghead, I remember seeing a device which is like an
>easle with a frame to hold a hand held scanner. It came bundled with
>software which would convert a grey-scale scanner to a color scanner.
>All one would have to do  is put a color picture under the scanner,
>pass it over the picture three times and the software would generate
>a color picture. Of course this was only availible for IBM compatible
>computers. What I'd like to know is if this same technology could
>work on a GS. I've already got a Quickie scanner and it does an
>excellent job in scanning grey scale, but to color a picture in a
>paint program requires a big effort.
> 
Well, of course it would work on the GS.  What they were doing (and
apparently this is internal) is using different color filters (or light
sources) for each scan and then using software to combine the images.
CCD cameras are typically most sensitive in the yellow-green range, which
accounts for the yellow-green light source seen in most scanners.  One could
make a set of red, green, and blue filters that fit over the scanner window,
but if the light source isn't sufficiently white, this wouldn't work well.
One has to make allowances in the different intensity levels registered 
for each color to make the final image look right, but that can be handled 
by software too.  It may lower the total color resolution since for a low
level signal, the entire value would correspond to only the few MSB's of a
stronger signal.  (I.E. Blue may give values of 0-16 while yellow might 
have a range of 0-128 in intensity.  To put them on the same scale requires
dividing the yellow by 8 and loosing the 3 LSB's.  (Note, 3 bits of resolution
for each of three colors would allow for 512 colors, so it's no big deal if
you don't get the full resolution of the scanner.  8 bits WOULD be nice; that's
16 MEGS of colors!!  (16,777,216 colors))
>
>Herbert Fung              herbertf@ersys.edmonton.ab.ca 

Michael Foegelle

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