[Insight-users] logarithmic intensity transformation

[Renaud Isabelle]

Hi,
 
I already knew about GetPixel() and SetPixel() methods as well as iterators to access the value of one pixel of my image. 
 
But is there already a method which enables me to retrieve the pixel data of my image directly in one matrix, such as GetBuffer or something like that? Maybe this is not the ideal but I was more familiar with having data stocked in one matrix and accessing pixel data via for loop and  so on.... 
 
Isabelle

Jakub Bican <jakub.bican at matfyz.cz> a écrit :


Hi Isabelle

How to access the pixel data is described in the ITK Software Guide

http://www.itk.org/ItkSoftwareGuide.pdf

Look for the chapter 4.1.3 "Accessing Pixel Data" (page 38).

You can also use more efficient way - iterators. See chapter 11 
"Iterators" (page 687).

Regards,
Jakub.



Renaud Isabelle napsal(a):
> Hi Jakub,
> 
> I took a look on your filter. However, I think there was a 
> misunderstanding.
> 
> I don't want to perform a pixel-wise log operation on my image.
> 
> Actually, I want to perform a kind of histogram transform called 
> *histogram logarithmic* to improve the contrast of my image.
> 
> So far, I performed histogram usual rescaling to transform my 
> intensities into the interval 0-255. Now, I would like my distribution 
> of gray intensities would be adjusted to improve contrast like:
> 
> f`'(x,y) = f min * (fmax / fmin) * P(f(x,y)) where P is the cumulated 
> histogram.
> 
> So adaptor will not help me, because this is an overall transform of the 
> image. Maybe I have to create my own filter but how can I access the 
> matrice of my pixel data form my image?
> 
> thanks,
> 
> Isabelle
> 
> 
> */Jakub Bican /* a écrit :
> 
> 
> Hi Isabelle,
> 
> logarithmic scaling can be done by these filters:
> 
> LogImageFilter (
> http://www.itk.org/Doxygen/html/classitk_1_1LogImageFilter.html )
> Log10ImageFilter (
> http://www.itk.org/Doxygen/html/classitk_1_1Log10ImageFilter.html )
> 
> and/or adaptors:
> 
> LogImageAdaptor (
> http://www.itk.org/Doxygen/html/classitk_1_1LogImageAdaptor.html )
> Log10ImageAdaptor (
> http://www.itk.org/Doxygen/html/classitk_1_1Log10ImageAdaptor.html )
> 
> Hope this will help you.
> 
> Regards,
> Jakub
> 
> 
> Renaud Isabelle napsal(a):
> 
> > Hi Luis,
> >
> > In one of your numerous posted replies, you already mentioned the
> use
> > of *logarithmic scaling* to improve visualisation of images.
> >
> > "It is not rare to use a logarithmic intensity transformation in
> order
> > to display the FFT output and still be able to "see" something."
> >
> http://public.kitware.com/pipermail/insight-users/2004-November/011201.html
> >
> > This is actually what I need to do to improve the quality of my
> > ultrasonographic image.
> >
> > --> Could you tell me a way to perform this logarithmic scaling? Is
> > there already a function for that, or maybe could I compute my
> own one
> > if you tell me how to get access of the pixel data of my image
> > displayed with ITK and VTK.
> >
> > Thanks for answer,
> >
> > Isabelle
> >
> >
> ------------------------------------------------------------------------
> > *Appel audio GRATUIT partout dans le monde* avec le nouveau Yahoo!
> > Messenger
> > Téléchargez le ici !
> >
> >
> >
> >------------------------------------------------------------------------
> >
> >_______________________________________________
> >Insight-users mailing list
> >Insight-users at itk.org
> >http://www.itk.org/mailman/listinfo/insight-users


		
---------------------------------
 Appel audio GRATUIT partout dans le monde avec le nouveau Yahoo! Messenger
 Téléchargez le ici !  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://public.kitware.com/pipermail/insight-users/attachments/20050629/63405466/attachment.htm