| combining color tables [message #60717] |
Sun, 08 June 2008 06:02 |
jochem.verelst@gmail.
Messages: 19
Registered: January 2007
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Junior Member |
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Hi IDL gurus,
A color question. In an image I wish to show the values until a
threshold (e.g. 1) in one color gradient (e.g. red) and the values
from this threshold onwards into another color gradient (e.g. blue).
In the newsgroup I found the following suggestion with code to combine
2 color tables. However, to me, only the color gradient of the last
loaded color table is shown.
;Why not use two different colormaps altogether...
im=randomu(sd,100,100)*10 ; some fake data
;; Load red into upper half of color map, and blue into the lower half
loadct,3,BOTTOM=!D.N_COLORS/2; red
loadct,1,NCOLORS=!D.N_COLORS/2;blue (only this color table is shown)
;; the upper half
dpos=bytscl(im,MIN=1.,TOP=!D.N_COLORS/2-1)+!D.N_COLORS/2
;; the lower half, in reverse!
dneg=!D.N_COLORS/2-1-bytscl(im,MAX=1.,TOP=!D.N_COLORS/2-1)
;; Put them together
d=dpos*(im ge 1.)+dneg*(im lt 1.)
tvimage, d
Can someone help me out? I also wish to show a color bar.
greetzz, Jochem
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