Noise filter

Noise filter

Post by John » Thu, 20 Dec 2007 20:09:02


Hello,

I would like to implement noise filters for scanned document.
I mean Dust and Scratches, Despeckle and Median filters.

Any sample somewhere ?

Thanks

John
 
 
 

Noise filter

Post by Nils Haec » Fri, 21 Dec 2007 11:12:31

Hi John,

Perhaps you should provide a link to some of the images you want to filter
for noise, so we can get an idea.

It really depends on what size the dust and scratches are, and how easily
they can be distinguished from real content.

Usually to filter noise, you need some edge-preserving smoothing filter. One
very interesting article I read was about the SUSAN filter.
http://www.yqcomputer.com/

Nils

"John" < XXXX@XXXXX.COM > schreef in bericht

 
 
 

Noise filter

Post by Rabatscher » Fri, 21 Dec 2007 16:52:24

I once saw a demo using a "Total Variation" approach. It is
computational very intense since it is an iterative approach, but
can be implemented on graphics cards (e.g. with CUDA) and is very
good for edge preserving noise reduction (The demo showed the
restauration of a picture containing more than 70 percent
noise).

Another approach could be mean shifting the image to find the
edges in a quite robust way. Remove the edges from the picture,
apply a filter routine to reduce the noise and add the edges
again to the image.

kind regards
Mike
 
 
 

Noise filter

Post by John » Fri, 21 Dec 2007 17:53:28

Hi Nils,

I think you should be able to see such feature here :
http://www.yqcomputer.com/

regards

John
 
 
 

Noise filter

Post by Nils Haec » Sat, 22 Dec 2007 07:35:14

This is a complete manual.. I still don't know what you want :) If you want
specific answers you have to ask specific questions.

Nils
 
 
 

Noise filter

Post by David Ninn » Sat, 22 Dec 2007 09:33:33


There's a despeckle in GIMP - online code is here
http://www.yqcomputer.com/
the despeckle_median routine seems to be the one that does the work.

A median filter is related there's a description here
http://www.yqcomputer.com/

hth,
Dave
 
 
 

Noise filter

Post by John » Tue, 25 Dec 2007 17:31:53

Houps...page 21 to 24...