[Insight-users] Initial level set capture

[Luis Ibanez]

Hi Jayant,

2) You could use the itkRescaleIntensityImageFilter for
    rescaling the speed image. If you instantiate this filter
    for having an "unsigned char" image as output, you will
    be able to save that image in PNG, JPEG and TIFF formats
    among others.

    Note that you could also, download ParaView and use it
    for visualizing 2D and 3D MetaImage.  You can download
    binary versions of ParaView from

        http://www.paraview.org

   Source code is also freely available.

   Once you load your speed image in paraview, you can easily
   generate iso-contours on it in order to study the distribution
   of gray levels. You can also use native colormaps in paraview
   in order to visualize the intensity distribution.


3) The isovalue only matters for interpreting the input
    image that is passed as initial level set to the
    GeodesicActiveContours filter.  For example, you can
    pass a char image with values from 0 to 255 and say that
    the iso-value you are interested on is at 123.

    If you want to see how this affects your level set computations,
    simply threshold the image at that level and visualize it.
    The shape that you will see, is what you are passing to the
    GeodesicActiveContours filter.

4) Your description was quite confusing...
    But... from it,... it seems that you are passing a contour
    as initial level set instead of passing a solid figure...
    I couldn't see how you get two rectangles, one going inwards
    and the other one going outwards.
    Maybe you will have to post a couple of images in order to
    illustrate this behavior.


Regards,


   Luis


------------------------
Jayant Chauhan wrote:

> 
> I have finally been able to use GeodesicActiveContourImageFilter, and
> after setting the isovalue to anything other than 0, I get results, that
> is, I get my contour close to the edges, but not exactly on them.
>  
> 1) Could some one please tell me if there is a way of storing the contour
> (using ZeroCrossingFilter) after each iteration, ie, if I run my progrm
> with the stopping criteria being RMS = 0.002 and max no of iteration =
> 1000, could I in any way store the contours at a periodic step, say after
> every 5 iterations. I finally want to see the movement of the contour.
>  
> 2)Another problem I am stuck with is that I want to see the SPEED image, but
> can do it only by saving it as a .mha or vtkimage. But I am having trouble
> compiling ImageViewer code. Is there no other way of doing this ?? Maybe
> changing the speed image in a way so that I can may save it as a PNG file
> ?? maybe color codes for -ive and +ive??? I really dont know how the speed
> image looks like.
> 3) Another query is regarding the ISOVALUE, how do we decide the ISOVALUE, I
> am getting results for ISOVALUE being anything other than ZERO,
> If I keep isovalue = 0, it seems the contour stops after sometime, as if
> stuck.
> 4) My last query is regarding my initial level set which I had created 
> in Matlab like this :
>       initlevel = zeros(240,320);
>       initlevel(40:225,99) = -1.8;
>       initlevel(40:225,100) = 1.0;
>  
>       initlevel(40:225,251) = -1.8;
>       initlevel(40:225,2500) = 1.0;
>  
>       initlevel(39,100:250) = -1.3;
>       initlevel(40,100:250) = 1.3;
>  
>       initlevel(225,100:250) = 1.6;
>       initlevel(226,100:250) = -0.9;
>  
> I have also set the ReverseExpansionDirection on, using SetRever...(true);
>  
> Now when I start the iterations, the contour seems to be moving in both 
> the directions, that is instead of one rectangle, I now have 2 
> rectangles, one moving inwards and the other moving outwards, but the 
> fact is that the object lies inside the initlevelset (as I am using the 
> difference image) and there nothing outside. Can anyone help me with this ??
>  
>  
>  with regards
> Jayant Chauhan
> 
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