[Insight-users] RecursiveGaussianImageFilter problems

[Luis Ibanez]

Hi Bjorn,

You may also use  the itkRescaleIntensityImageFilter in order
to transform the intensity scale of an image and make it fit in
a particular range.   The filter requires that you provide the
range for the output.


   SetOutputMinimum()
  SetOutputMaximum();

That will be easier than combining the MinimumMaximumImageFilter
and the ShiftScaleImageFilter.


 
     Luis



===========================================
Luis Ibanez wrote:

>
> Hi Bjorn,
>
> Its good to know that the pixel type problem was solved !,
>
>
> About converting the image that you generated
> into a potential map:
>
> According to the text in the URL that you indicated, you seem
> to be computing the Laplacian of the original image.
> (It wasn't clear where  the DiscreteGaussianFilter was used though...)
>
> If what you obtain is the Laplacian of your image, it will have 
> positive and
> negative values around the edges and will have near zero values in 
> monotonic
> regions. So it seems that the only thing missing is to rescale the 
> intensity
> values from [min,max] to [-1,1].
>
> You can use the two following filters combined:
>
> itkMinimumMaximumImageFilter
> http://www.itk.org/Doxygen/html/classitk_1_1MinimumMaximumImageFilter.html 
>
>
> itkShiftScaleImageFilter
> http://www.itk.org/Doxygen/html/classitk_1_1ShiftScaleImageFilter.html
>
> The first will compute the maximum and minimum values in
> intensity of your image. The second will allow you to apply pixel-wise
> a linear transformation on the intensity of the image.
>
> The itkMinimunMaximumImageFilter is a bit particular in that
> the output image is identical to the input image. It actual useful
> values are the ones that you get with:
>
> GetMaximum() and GetMinimum().
>
> Using this two values you can update the itkShiftScaleFilter input
> parameters in order to set the linear transform that will map the
> intensity values to  [-1,1].
>
>
> This connection will require that you hard code the intensity
> transform.  This is due to a temporary limitation in ITK pipeline
> mechanism which doen't allow yet to pass data different from
> Images and Meshes.   This is being analyzed so hopefully we
> will be able soon to pass types like integers, floats, transforms,
> points... etc through pipeline connections of the type
>
>        a->GetInput(  b->GetOuput() )
>
>
>
> Please let us know if you find any problem by doing this
> intensity transformation.
>
>
>   Thanks
>
>
>      Luis
>
>
> =============================================================
>
> Bjorn Hanch Sollie wrote:
>
>>> What is the pixel type that you are using for you ImageType ?
>>>
>>
>> I'm using floats, which is why I didn't understand the palette
>> distortion.  As it turned out, it was a cast at a different spot in my
>> code that caused the problem.  It is now fixed, and the filter appears
>> to work.  Thanks for helping me out!  The quite pleasing result may be
>> beholded at:
>>
>>   <URL:http://www.pvv.org/~bhs/edge.html>
>>
>> Howver this makes for another problem: The filtered edge image above
>> is quite difficult to use as a potential image for the
>> FastMarchingImageFilter, which is what I was aiming for in the first
>> place.  The potential image needs to be close to 1 at the edges and
>> close to 0 in monotonous regions, but with both the high and low
>> extremas in intensity occuring near or around the edges in this image,
>> it appears to be difficult to convert this image into a potential map.
>> Except for this problem, I appear to be quite close to my goal, in the
>> sense that the image does contain the edges I've been looking for.
>> Does anyone have any suggestions on how I can do this?  (Thresholding
>> is simple, but a bit too dangerous I fear...)
>>
>> -Bjorn
>>
>
>
>
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