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Re: Fanning's LogScl routine + Colorbar?? [message #71841 is a reply to message #71837]

Fri, 23 July 2010 10:46

pgrigis
Messages: 436
Registered: September 2007

Senior Member

On Jul 23, 1:23 pm, Joe Daal <joe.d...@gmail.com> wrote:
> Hi,
>
> I am using the logscl to enhance the contrast of an image, something
> like:
>
> loadct,39
> image = alog10(lin_image)
> imdisp, logscl(image, min=min(image), max=max(image), Exponent=8,
> Mean=0.65)
>
> where image values vary from -1.34 to +2.05, with zeroes included.
> The image looks nice for what I want, but how do I reflect a correct
> colorbar, either for real values or the scaled ones? What is
> logarithmic, the ticks or the colors?

Hi,

I would argue for both.

Example using
http://hea-www.cfa.harvard.edu/~pgrigis/idl_stuff/pg_plotima ge.pro
below will show different color bars.

;create color bar array
x=findgen(1000)
y=findgen(256)
z=rebin(x,1000,256)

;case 1: log axis and log colors - that's what you want
pg_plotimage,alog(z),x,y,xrange=[1,1000],/xlog,/ylog,yrange= [1,255],/
xsty,/yst

;case 2: linear axis and log colors
;this is a "correct" but undesirable representation: the beholder of
the plot will
;not be able to make out the colors for low values of the x axis
pg_plotimage,alog(z),x,y,xrange=[1,1000],/ylog,yrange=[1,255 ],/xsty,/
yst

;case 3: linear axis and linear colors - this is what happens if you
do not log scale the image
pg_plotimage,z,x,y,xrange=[1,1000],/ylog,yrange=[1,255],/xst y,/yst

;case 4: log axis and linear colors - this is what happens if you do
not log scale the image
;but is shown in a not particularly useful representation
pg_plotimage,z,x,y,xrange=[1,1000],/ylog,yrange=[1,255],/xst y,/yst,/
xlog

Ciao,
Paolo
>
> Thanks,
> Joe

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[Message index]

		Re: Fanning's LogScl routine + Colorbar?? By: David Fanning on Sat, 24 July 2010 08:40
		Re: Fanning's LogScl routine + Colorbar?? By: David Fanning on Fri, 23 July 2010 13:32
		Re: Fanning's LogScl routine + Colorbar?? By: pgrigis on Fri, 23 July 2010 13:10
		Re: Fanning's LogScl routine + Colorbar?? By: pgrigis on Fri, 23 July 2010 12:53
		Re: Fanning's LogScl routine + Colorbar?? By: pgrigis on Fri, 23 July 2010 12:51
		Re: Fanning's LogScl routine + Colorbar?? By: David Fanning on Fri, 23 July 2010 12:38
		Re: Fanning's LogScl routine + Colorbar?? By: pgrigis on Fri, 23 July 2010 10:46
		Re: Fanning's LogScl routine + Colorbar?? By: pgrigis on Mon, 26 July 2010 07:59
		Re: Fanning's LogScl routine + Colorbar?? By: Joe Daal on Wed, 28 July 2010 20:47

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