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Re: color mapping question [message #6809 is a reply to message #6806]

Thu, 29 August 1996 00:00

Liam Gumley
Messages: 473
Registered: November 1994

Senior Member

Scott Gennari wrote:
> I have a 256 color grayscale image and i'd like to overlay a
> coastline with some color (red). How would I strech the grayscale
> data values to fit 0-254 and reserve value 255 for a certain rgb
> color? I'm Not having much luck with STRETCH,0,254 and then assigning
> a rgb color to 255.

Try something this:

;- load grey scale color table

loadct,0

;- display image scaled to full color range, leaving one color
;- free at top of lookup table

tv,bytscl(dist(256),top=!d.n_colors-2)

;- make top color in lookup table red

tvlct,r,g,b,/get
g(!d.n_colors-1)=0
b(!d.n_colors-1)=0
tvlct,r,g,b

;- overplot a line in red

plots,[0,0],[200,200],color=!d.n_colors,/device

Cheers,
Liam.

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[Message index]

		color mapping question By: gennari on Thu, 29 August 1996 00:00
		Re: color mapping question By: Liam Gumley on Thu, 29 August 1996 00:00
		Re: color mapping question By: Christian Soeller on Thu, 29 August 1996 00:00
		Re: color mapping question By: David Foster on Thu, 29 August 1996 00:00

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