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Re: How to eliminate smaller blob from label_region image [message #77346 is a reply to message #77335]

Mon, 22 August 2011 05:37

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Wox writes:

>
> On Sun, 21 Aug 2011 22:40:24 -0700 (PDT), vijay s
> <vijayans.in@gmail.com> wrote:
>
>> hi all,
>>
>> I used label_region to get individual blob id for each region.
>> But few of my blobs are very small in area wise and
>> i want to eliminate those from my images and retain blobs of larger
>> area (say pixel area gt 10). How can i eliminate unwanted smaller
>> blobs?
>>
>>
>> thanks in advance.
>
>
> By using the HISTOGRAM function:
>
>
> ; Minimum number of blob pixels
> npix_threshold=10
>
> ; Get image
> path=FILEPATH('pollens.jpg',SUBDIR=['examples','demo','demod ata'])
> READ_JPEG, path, image
>
> ; Get blob indices
> b = LABEL_REGION(image gt 150)
>
> ; Get population and members of each blob
> h = HISTOGRAM(b, REVERSE_INDICES=r)
>
> ; Regions with small number of pixels
> ind = where(h lt npix_threshold,ct)
>
> ; Remove the small regions
> for i=0l,ct-1 do b[r[r[ind[i]]:r[ind[i]+1]-1]]=0
>
>
> Obviously, some indices will be missing since you zero'ed them out.
> You might want to fix that. It might not even be necessary to set the
> small blob indices to zero. It all depends on what you will do with
> the blob indices.

This is the method used by the Blob_Analyzer, and it makes
it trivial to deal with blobs below a specific size.

theBlobs = Obj_New('Blob_Analyzer', biLevelImage)
nBlobs = theBlobs -> NumberOfBlobs()
FOR j=0,nBlobs-1 DO BEGIN
indices = theBlobs -> GetIndices(j, COUNT=count)
IF count LE 10 THEN Continue

.... ; Else, do your thing.

ENDFOR

You can find information on the Blob_Analyzer here:

http://www.idlcoyote.com/ip_tips/blobanalysis.html

Cheers,

David

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

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[Message index]

		Re: How to eliminate smaller blob from label_region image By: David Fanning on Tue, 23 August 2011 05:02
		Re: How to eliminate smaller blob from label_region image By: Wout De Nolf on Tue, 23 August 2011 04:18
		Re: How to eliminate smaller blob from label_region image By: vijay s on Mon, 22 August 2011 23:30
		Re: How to eliminate smaller blob from label_region image By: David Fanning on Mon, 22 August 2011 05:37
		Re: How to eliminate smaller blob from label_region image By: Wout De Nolf on Mon, 22 August 2011 01:13
		Re: How to eliminate smaller blob from label_region image By: rogass on Wed, 31 August 2011 05:00

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