[Insight-users] SignedDanielssonDistanceMapImageFilter

Wed Dec 10 15:46:14 EST 2008

Hi, Luis.

Thanks for the clarification.
My purpose is to build a signed distance function given a point clouds of a shape boundary. I know there are several options to do this. If the only input are those points, which is the best, fast and easiest way to do this? I know there are several options in ITK.
1.  FastMarching.  
2.  Reinitiaze
3.  DistanceMap (Danielsson).

Another question would be regarding smart pointer and raw pointer.  Is it OK to return a smart pointer from a function?
E.g. I have this code:
//////////////////////////////////////////////////////////////////////
main.cpp
typedef itk::Image< unsigned char, 2 > BinaryImageType;typedef itk::Image< float , 2> LSVImageType;LSVImageFilter::Pointer LSVImage =  SDF(contour) // where the contour is binary image

SDF.cpp
LSVImageType::Pointer SDF(BinaryImageType::Pointer contour)
{       typedef itk::SignedDanielssonDistanceMapImageFilter < BinaryImageFilter, LSVImageFilter > FilterType;       FilterType::Pointer filter = FilterType::New();        filter ->SetInput ( contour ); // contour is the binary image 
       return filter->GetOutput();
} 
//////////////////////////////////////////////////////////////////////

Thanks for any input
Siqi

> Date: Wed, 10 Dec 2008 15:16:08 -0500> From: luis.ibanez at kitware.com> To: pidanchen at hotmail.com> CC: insight-users at itk.org> Subject: Re: [Insight-users] SignedDanielssonDistanceMapImageFilter> > > Hi Chensiqi,> > You are misinterpreting the behavior of this filter.> > If you have a binary image, where> > * The foreground object is set to 1 and> * The background object is set to 0> > > Then the SignedDanielssonDistanceMapImageFilter will compute> the distances to the *transition* region between the 0s and> the 1s.> > All pixesl in the 0s region will have positive distances to> that boundary, while all pixels in the 1s region will have> negative distances to that boundary.> > In your case you are feeding an input image where the *boundary*> points are set to 1. Therefore, there is no "inside" to the> object.> > E.g. if you are feeding into this distance filter an image with> a thin ring, you are not going to find the "inside" of the ring.> > You should feed this filter with an image containing a filled> circle of radius R. Where all the points at locations r < R will> be set to 1s. Only in that case will the distance map be able to> find the "inside" of the object.> > > Regards,> > > Luis> > > ---------------> chensiqi wrote:> > Hi, Ghassan> > > > Thanks for the advice. I flip the input.> > The result now is both inside and outside are positive :(> > > > I use float type as the filteroutput instead of "unsigned short" in the > > example. I also tried unsigned short, the result is the same.> > > > Here is part of my code. > > ////////////////////////////////////////////////////////////////////////////////////////////////////> > typedef itk::Image< unsigned char, 2 > BinaryImageType;> > typedef itk::Image< float , 2> LSVImageType;> > typedef itk::SignedDanielssonDistanceMapImageFilter < BinaryImageFilter, > > LSVImageFilter > FilterType;> > FilterType::Pointer filter = FilterType::New();> > > > filter ->SetInput ( contour ); // contour is the binary image with > > BinaryImageType, 1 at boundary points, and 0 elsewhere.> > > > LSVImageFilter::Pointer LSVImage = filter->GetDistanceMap();> > > > Display (LSVImage) // this is a function that displays the image.> > //////////////////////////////////////////////////////////////////////////////////////////////////////> > > > I notice when I cout<<LSV_image->GetBufferedRegion().GetSize() , the > > output is [0,0]. I guess there is something wrong in my code that > > causes this weird output size. I can display LSVImage, although both > > inside and outside region are postive.> > > > > > Thanks for any input> > Siqi> > > > > CC: insight-users at itk.org> > > From: hamarneh at gmail.com> > > To: pidanchen at hotmail.com> > > Subject: Re: [Insight-users] SignedDanielssonDistanceMapImageFilter> > > Date: Tue, 9 Dec 2008 20:45:19 -0800> > >> > > Hello Siqi,> > >> > > You write: "The input is only a binary image with boundary points at> > > 0, and all other points at 1."> > > However, according to he documentation: "As a convention, the distance> > > is evaluated from the boundary of the ON pixels."> > > (from > > http://www.itk.org/Doxygen/html/classitk_1_1SignedDanielssonDistanceMapImageFilter.html > > > > > )> > > So, your input image should have boundary pixels set to 1 and all> > > other points to 0 (and not the other way around).> > > HTH,> > > /Ghassan> > >> > >> > >> > > On 9-Dec-08, at 7:24 PM, chensiqi wrote:> > >> > > >> > > > Hi, ITKers> > > >> > > > I got two ques tions regarding SignedDanielssonDistanceMapImageFilter.> > > >> > > > 1. The result I have is not "signed", both the inside and outside> > > > distance values are negative. The input is only a binary image with> > > > boundary points at 0, and all other points at 1. I was wondering> > > > how I was wondering how SignedDanielssonDistanceMapImageFilter> > > > determine the region of inside and outside.> > > >> > > > 2. In Examples of SignedDanielssonDistanceMapImageFilter. cxx, I> > > > notice that the OutputImageType of filter is unsigned short, which I> > > > don't quite understand. The output should contains both negative> > > > and positive distance, why use "unsigned" here?> > > >> > > > Thanks> > > > Siqi> > > >> > > > MSN保护盾，十八般武艺保障MSN安全！ 现> > > > 在就下载！ _______________________________________________> > > > Insight-users mailing list> > > > Insight-users at itk.org> > > > http://www.itk.org/mailman/listinfo/insight-users> > >> > > > > > ------------------------------------------------------------------------> > MSN热搜榜全新升级，更多排行榜等着你！ 立即查看！ < http://top.msn.com.cn>> > > > > > ------------------------------------------------------------------------> > > > _______________________________________________> > Insight-users mailing list> > Insight-users at itk.org> > http://www.itk.org/mailman/listinfo/insight-users
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