| Re: color .ps/gamma_ct [message #10811 is a reply to message #10809] |
Fri, 23 January 1998 00:00   |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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Peter Gallagher wrote:
>
> Hi all,
>
> I'm trying to plot two images in one Postscript file using the
> same color table. The only problem is that I want to apply a
> different gamma correction to each image.
>
> Something like ...
>
> LOADCT, 3
>
> TV, image1
> GAMMA_CT,.7
>
> TV, image2
> GAMMA_CT,.3
>
> The GAMMA_CT changes the appearance of both the images each time
> it is applied - I want a separate gamma correction for each image.
>
> Any body come up against this problem before?
>
No, but having just read this part in David Fanning's excellent book,
I would assume you will have to try the following steps:
1) load your color table
2) apply the 1st gamma correction
3) read the color table into an array (or the 3 r,g,b arrays)
4) load the original color table again
5) apply the second gamma correction
6) read the color table into an array
7) shrink both arrays by eliminating every second entry
8) load array1 in the lower part of the color table
9) load array2 in the upper part of the color table
10) re-scale your images (BYTSCL) so that they span the color
range of 0..half-1 (image1) and half..top (image2)
Hope this helps,
Martin.
------------------------------------------------------------ -------
Dr. Martin Schultz
Department for Earth&Planetary Sciences, Harvard University
186 Pierce Hall, 29 Oxford St., Cambridge, MA-02138, USA
phone: (617)-496-8318
fax : (617)-495-4551
e-mail: mgs@io.harvard.edu
IDL-homepage: http://www-as.harvard.edu/people/staff/mgs/idl/
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