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Re: Function BYTSCL [message #24644 is a reply to message #24641]

Tue, 10 April 2001 03:08

marc schellens[1]
Messages: 183
Registered: January 2000

Senior Member

Steffen Kernchen wrote:
>
> Hi...
>
> Iï¿½m just starting with IDL, so here is my first question: ;-)
>
> what function(s) can I use instead of BYTSCL?
> I have an array and I want to transform it to get a better contrast.
> But I should NOT use BYTSCL.... :(
>
> bye
>
> steffen

Of course you can do by hand something similar what bytscl does:

lets say your array is 'a'

minA=min(a,MAX=maxA)
a=a-minA
a=byte(float(a)/maxA*255)

(2nd line is 'optional')
but why you should not use bytarr?
Only point I can guess is that you have 8bit color and dont want to
use all colors?
In that case you have to find the different used colors in a:

h=histogram(a)
wN0=where(h ne 0,nW)

replace them:

for i=0,nW-1 do begin
wI=where(a eq wN0[i])
a[wI]=i
endfor

and modify the color table to assign the remaining values to colors
0..255:

TVLCT, R, G, B, /GET

R[0:nW-1]=byte(float(indgen(nW))/nW*255)
G[0:nW-1]=byte(float(indgen(nW))/nW*255)
B[0:nW-1]=byte(float(indgen(nW))/nW*255)

TVLCT, R, G, B

then you can plot your image.

Cheers,
marc

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[Message index]

		Re: Function BYTSCL By: marc schellens[1] on Tue, 10 April 2001 18:20
		Re: Function BYTSCL By: davidf on Tue, 10 April 2001 16:43
		Re: Function BYTSCL By: davidf on Tue, 10 April 2001 10:18
		Re: Function BYTSCL By: Jaco van Gorkom on Tue, 10 April 2001 09:37
		Re: Function BYTSCL By: davidf on Tue, 10 April 2001 08:10
		Re: Function BYTSCL By: Liam E. Gumley on Tue, 10 April 2001 07:44
		Re: Function BYTSCL By: Steffen Kernchen on Tue, 10 April 2001 07:42
		Re: Function BYTSCL By: davidf on Tue, 10 April 2001 07:30
		Re: Function BYTSCL By: Jaco van Gorkom on Tue, 10 April 2001 07:18
		Re: Function BYTSCL By: davidf on Tue, 10 April 2001 06:55
		Re: Function BYTSCL By: marc schellens[1] on Tue, 10 April 2001 03:08
		Re: Function BYTSCL By: Steffen Kernchen on Tue, 10 April 2001 03:51
		Re: Function BYTSCL By: davidf on Tue, 10 April 2001 03:17

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