| Re: combining color tables [message #60698] |
Mon, 09 June 2008 23:52  |
jochem.verelst@gmail.
Messages: 19
Registered: January 2007
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Junior Member |
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On Jun 9, 4:13 pm, Jeremy Bailin <astroco...@gmail.com> wrote:
> On Jun 8, 9:02 am, "jochem.vere...@gmail.com"
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> <jochem.vere...@gmail.com> wrote:
>> 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
>
> I think you want !D.TABLE_SIZE (the number of entries in the colour
> table) instead of !D.N_COLORS (the number of different colours
> possible in the display).
>
> -Jeremy.- Hide quoted text -
>
> - Show quoted text -
Rigth, now it works perfectly :) Thanks a lot. Also thanks for the
suggestion of checking the Brewer color tables. They are very nice.
grtzz, Jochem
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