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Re: combining color tables [message #60709 is a reply to message #60698]

Mon, 09 June 2008 07:13

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On Jun 8, 9:02 am, "jochem.vere...@gmail.com"
<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.

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[Message index]

		Re: combining color tables By: jochem.verelst@gmail. on Mon, 09 June 2008 23:52
		Re: combining color tables By: Jeremy Bailin on Mon, 09 June 2008 07:13
		Re: combining color tables By: russell.grew on Sun, 08 June 2008 15:36

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