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Re: Stretching an image [message #41950]

Fri, 10 December 2004 10:41

Liam Gumley
Messages: 473
Registered: November 1994

Senior Member

David Fanning wrote:
> Liam Gumley writes:
>
>
>> I believe ENVI uses what is known as histogram clipping, as a way to
>> remove outlier values from the stretch range. I describe an
>> implementation of histogram clipping in Chapter 7 of my book. Here is
>> the code from the book (imclip.pro):
>>
>> ;---start of imclip.pro---
>> FUNCTION IMCLIP, IMAGE, PERCENT=PERCENT
>>
>> ;- Check arguments
>> if (n_params() ne 1) then $
>> message, 'Usage: RESULT = IMCLIP(IMAGE)'
>> if (n_elements(image) eq 0) then $
>> message, 'Argument IMAGE is undefined'
>>
>> ;- Check keywords
>> if (n_elements(percent) eq 0) then percent = 2.0
>>
>> ;- Get image minimum and maximum
>> min_value = min(image, max=max_value)
>>
>> ;- Compute histogram
>> nbins = 100
>> binsize = float(max_value - min_value) / float(nbins)
>> hist = histogram(float(image), binsize=binsize)
>> bins = lindgen(nbins + 1) * binsize + min_value
>
>
> Liam, why 100 bins? I would have thought the minimum
> number would be 256, to correspond with a possible byte
> image. Or is 100 just a nice round number that gives
> reasonable results?
>
> Cheers,
>
> David

A nice round number that gives reasonable results.

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[Message index]

		Re: Stretching an image By: Liam Gumley on Fri, 10 December 2004 10:41
		Re: Stretching an image By: David Fanning on Fri, 10 December 2004 08:33
		Re: Stretching an image By: Liam Gumley on Fri, 10 December 2004 07:14
		Re: Stretching an image By: David Fanning on Thu, 09 December 2004 13:36
		Re: Stretching an image By: KM on Thu, 09 December 2004 13:33
		Re: Stretching an image By: jnettle1 on Thu, 09 December 2004 11:51
		Re: Stretching an image By: David Fanning on Thu, 09 December 2004 11:01
		Re: Stretching an image By: KM on Fri, 10 December 2004 13:15

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