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Re: Get min and max values from a multiband image according to pixel locations of classification image [message #82055]

Sat, 17 November 2012 07:53

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

> class1Pixels = Where(classifiedImage EQ class1, count)
> IF count GT 0 THEN BEGIN
> class1Min = minImage[class1Pixels]
> class1Max = maxImage[class1Pixels]
> ENDIF

If your images are large, it is often MUCH faster
to use the Histogram command to locate classified
pixels. Assume, for example, that in your classified
image, the three classes are labeled with 1, 2, and 3.
Then:

h = Histogram(classifiedImage, BinSize=1B, Reverse_Indices=ri)
class1Pixels = Reverse_Indices(ri, 1, COUNT=cnt1)
class2Pixels = Reverse_Indices(ri, 2, COUNT=cnt2)

Etc.

You can find Reverse_Indices here:

http://www.idlcoyote.com/programs/reverse_indices.pro

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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		Re: Get min and max values from a multiband image according to pixel locations of classification image By: David Fanning on Sat, 17 November 2012 07:53
		Re: Get min and max values from a multiband image according to pixel locations of classification image By: David Fanning on Sat, 17 November 2012 07:40

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