| Re: problem with colors [message #47092] |
Thu, 19 January 2006 09:36 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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psbeps@hotmail.com writes:
> I have an IDL program that creates an image of sea surface temperature
> anomalies, where dark purple (almost black) is the cold anomalies and
> red is the warm anomalies. I have set up brown, blue, black, and white
> as color indices 252, 253, 254, and 255, respectively. The hottest
> anomalies were showing up as blue (this was before I added brown as a
> color), instead of red, which I think is because blue was the next
> color after red. So I changed the code from
> scaledc=bytscl(c, MIN=min(c), MAX=max(c), top=253) + byte(bottom)
> to
> scaledc=bytscl(c, MIN=min(c), MAX=max(c), top=251) + byte(bottom)
> because 251 is the last red color index. When the top is set to 251,
> the blue anomalies are red, which I think they should be. So that is
> good. The problem is that when I have top set to 251, it won't let me
> assign parts of the image to certain colors, like making the ice white
> or the land black. I think it's only by coincidence making the ice
> white and the land black, so I don't totally trust black areas are land
> and white areas are ice, although it looks plausible. It only will
> draw the 4 assigned colors where I want them, if the top value in the
> above line of code is equal to 256, to include the 4 assigned color
> indices. I want to be able to have the hottest anomalies be red (if
> top=251), but also I want to be able to make the land black and the ice
> white, and undetermined values black or brown (if top=256). How can I
> do both things? Here is the other relevant code:
> c(*,*)=scaledc(*,*)*(theIceflags(*,*) eq 0 and theLandflags(*,*) eq 0
> and theundflags(*,*) eq 0) + iceColor*(theIceflags(*,*) eq 1) +
> landColor*(theLandflags(*,*) eq 1) + landColor*(theundflags(*,*) eq 1)
> --where c is the sea surface temperature anomaly which should be
> purple, blue, yellow, orange, or red. My theIceflag array is 1's and
> 0's, where 0 means there is no ice, and 1 means there is ice. The same
> goes for theLandflags and theundflags.
Oh, dear. I'm off to Boulder, but you are byte scaling
your data incorrectly. Have a look at how I do it here.
http://www.dfanning.com/graphics_tips/toms_tutorial.html
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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