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Re: Rescaling byte (0-200) ndvi to -1 to 1 values [message #80861 is a reply to message #80855]

Thu, 19 July 2012 13:13

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Hello,

On 07/19/12 15:19, Narnia wrote:
> Thanks a lot, Paul, that makes sense of course but (I'm a real beginner with IDL), I'm still not sure how I would
> implement that as far as calling in the images and declaring that to run and scale all the images in my folder! :(

Well, let's assume you already have a function that reads the image data (I can't help with that one). Let's call it
"read_image" and assume it looks something like:

FUNCTION Read_Image, Filename
...open file...
...read image data...
RETURN, image_data
END

Your scaling function could look like

FUNCTION Scale_Image, Input_Image
output_image = FLOAT(Input_Image)
output_image = (output_image - 100.0) / 100.0
RETURN, output_image
END

Then you can loop over your filenames on the command line

IDL> files = FILE_SEARCH("path/to/data/emodis.filename.*")
IDL> FOR n = 0, N_ELEMENTS(files) DO BEGIN & scaled_image = Scale_Image(Read_Image(files[n])) & ...display... & ENDFOR

?

cheers,

paulv

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[Message index]

		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Fri, 20 July 2012 07:01
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Fri, 20 July 2012 07:05
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: David Fanning on Fri, 20 July 2012 06:07
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Fri, 20 July 2012 06:03
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Paul Van Delst[1] on Thu, 19 July 2012 13:13
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Narnia on Thu, 19 July 2012 12:19
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: Paul Van Delst[1] on Thu, 19 July 2012 11:41
		Re: Rescaling byte (0-200) ndvi to -1 to 1 values By: k.shemsu on Mon, 20 May 2013 05:39

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