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Re: COLOR_QUAN question [message #16770 is a reply to message #16763]

Thu, 19 August 1999 00:00

Daniel Peduzzi
Messages: 29
Registered: June 1999

Junior Member

David Fanning wrote in message ...
> Daniel Peduzzi (peduzzi@mediaone.net) writes:
>
>> My question concerns the R, G, and B arrays returned by the COLOR_QUAN
>> function. I've noticed that I don't receive the same RGB values if I call the function
>> multiple times with the same input arguments. This isn't very noticeable upon visual
>> inspection of the resulting images, unless the differences are exaggerated by color map
>> operations such as histogram equalization.
>
> Oh, oh. Hold on here. I think we may be fooling ourselves
> a bit. First of all, in the examples that matter (Step 1
> and Step 3) the first 31 colors are the gray scale colors
> of the images. They appear to be identical in both color
> tables. (I used my CINDEX program to view the color tables
> after I loaded them.) Moreover, the resulting 2D images
> only have values between 0 and 31, and *they* are
> identical.
>

Thanks...everything you said made perfect sense. However, I'm still a bit
confused about the purpose of the COLORS keyword. In STEP 1-3 of my
example, I specified COLORS=256 in each call to COLOR_QUAN. As you
pointed out, the digital values of each resulting image lie in the range [0,31].
If the COLORS keyword doesn't have any influence on the values in the image
returned by COLOR_QUAN, then what is it used for?

I guess I expected to see 256 entries in the output palette USED by the returned image.

Dan Peduzzi
peduzzi@mediaone.net

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[Message index]

		Re: COLOR_QUAN question By: steinhh on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: Liam Gumley on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: Struan Gray on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: Daniel Peduzzi on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: davidf on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: davidf on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: Struan Gray on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: davidf on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: Struan Gray on Thu, 19 August 1999 00:00
		Re: COLOR_QUAN question By: davidf on Wed, 18 August 1999 00:00

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