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<BR>Hi, Luis.<BR>
<BR>
Thanks for the clarification.<BR>
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.<BR>
1. FastMarching. <BR>
2. Reinitiaze<BR>
3. DistanceMap (Danielsson).<BR>
<BR>
Another question would be regarding smart pointer and raw pointer. Is it OK to return a smart pointer from a function?<BR>
E.g. I have this code:<BR>
//////////////////////////////////////////////////////////////////////<BR>
main.cpp<BR>
typedef itk::Image< unsigned char, 2 > BinaryImageType;<BR>typedef itk::Image< float , 2> LSVImageType;<BR>LSVImageFilter::Pointer LSVImage = SDF(contour) // where the contour is binary image
<BR>
SDF.cpp<BR>
LSVImageType::Pointer SDF(BinaryImageType::Pointer contour)<BR>
{<BR> typedef itk::SignedDanielssonDistanceMapImageFilter < BinaryImageFilter, LSVImageFilter > FilterType;<BR> FilterType::Pointer filter = FilterType::New(); <BR> filter ->SetInput ( contour ); // contour is the binary image <BR>
return filter->GetOutput();<BR>
} <BR><BR><BR>
//////////////////////////////////////////////////////////////////////<BR>
<BR>
<BR>
Thanks for any input<BR>
Siqi<BR>
<BR>
<BR>> Date: Wed, 10 Dec 2008 15:16:08 -0500<BR>> From: luis.ibanez@kitware.com<BR>> To: pidanchen@hotmail.com<BR>> CC: insight-users@itk.org<BR>> Subject: Re: [Insight-users] SignedDanielssonDistanceMapImageFilter<BR>> <BR>> <BR>> Hi Chensiqi,<BR>> <BR>> You are misinterpreting the behavior of this filter.<BR>> <BR>> If you have a binary image, where<BR>> <BR>> * The foreground object is set to 1 and<BR>> * The background object is set to 0<BR>> <BR>> <BR>> Then the SignedDanielssonDistanceMapImageFilter will compute<BR>> the distances to the *transition* region between the 0s and<BR>> the 1s.<BR>> <BR>> All pixesl in the 0s region will have positive distances to<BR>> that boundary, while all pixels in the 1s region will have<BR>> negative distances to that boundary.<BR>> <BR>> In your case you are feeding an input image where the *boundary*<BR>> points are set to 1. Therefore, there is no "inside" to the<BR>> object.<BR>> <BR>> E.g. if you are feeding into this distance filter an image with<BR>> a thin ring, you are not going to find the "inside" of the ring.<BR>> <BR>> You should feed this filter with an image containing a filled<BR>> circle of radius R. Where all the points at locations r < R will<BR>> be set to 1s. Only in that case will the distance map be able to<BR>> find the "inside" of the object.<BR>> <BR>> <BR>> Regards,<BR>> <BR>> <BR>> Luis<BR>> <BR>> <BR>> ---------------<BR>> chensiqi wrote:<BR>> > Hi, Ghassan<BR>> > <BR>> > Thanks for the advice. I flip the input.<BR>> > The result now is both inside and outside are positive :(<BR>> > <BR>> > I use float type as the filteroutput instead of "unsigned short" in the <BR>> > example. I also tried unsigned short, the result is the same.<BR>> > <BR>> > Here is part of my code. <BR>> > ////////////////////////////////////////////////////////////////////////////////////////////////////<BR>> > typedef itk::Image< unsigned char, 2 > BinaryImageType;<BR>> > typedef itk::Image< float , 2> LSVImageType;<BR>> > typedef itk::SignedDanielssonDistanceMapImageFilter < BinaryImageFilter, <BR>> > LSVImageFilter > FilterType;<BR>> > FilterType::Pointer filter = FilterType::New();<BR>> > <BR>> > filter ->SetInput ( contour ); // contour is the binary image with <BR>> > BinaryImageType, 1 at boundary points, and 0 elsewhere.<BR>> > <BR>> > LSVImageFilter::Pointer LSVImage = filter->GetDistanceMap();<BR>> > <BR>> > Display (LSVImage) // this is a function that displays the image.<BR>> > //////////////////////////////////////////////////////////////////////////////////////////////////////<BR>> > <BR>> > I notice when I cout<<LSV_image->GetBufferedRegion().GetSize() , the <BR>> > output is [0,0]. I guess there is something wrong in my code that <BR>> > causes this weird output size. I can display LSVImage, although both <BR>> > inside and outside region are postive.<BR>> > <BR>> > <BR>> > Thanks for any input<BR>> > Siqi<BR>> > <BR>> > > CC: insight-users@itk.org<BR>> > > From: hamarneh@gmail.com<BR>> > > To: pidanchen@hotmail.com<BR>> > > Subject: Re: [Insight-users] SignedDanielssonDistanceMapImageFilter<BR>> > > Date: Tue, 9 Dec 2008 20:45:19 -0800<BR>> > ><BR>> > > Hello Siqi,<BR>> > ><BR>> > > You write: "The input is only a binary image with boundary points at<BR>> > > 0, and all other points at 1."<BR>> > > However, according to he documentation: "As a convention, the distance<BR>> > > is evaluated from the boundary of the ON pixels."<BR>> > > (from <BR>> > http://www.itk.org/Doxygen/html/classitk_1_1SignedDanielssonDistanceMapImageFilter.html <BR>> > <BR>> > > )<BR>> > > So, your input image should have boundary pixels set to 1 and all<BR>> > > other points to 0 (and not the other way around).<BR>> > > HTH,<BR>> > > /Ghassan<BR>> > ><BR>> > ><BR>> > ><BR>> > > On 9-Dec-08, at 7:24 PM, chensiqi wrote:<BR>> > ><BR>> > > ><BR>> > > > Hi, ITKers<BR>> > > ><BR>> > > > I got two ques tions regarding SignedDanielssonDistanceMapImageFilter.<BR>> > > ><BR>> > > > 1. The result I have is not "signed", both the inside and outside<BR>> > > > distance values are negative. The input is only a binary image with<BR>> > > > boundary points at 0, and all other points at 1. I was wondering<BR>> > > > how I was wondering how SignedDanielssonDistanceMapImageFilter<BR>> > > > determine the region of inside and outside.<BR>> > > ><BR>> > > > 2. In Examples of SignedDanielssonDistanceMapImageFilter. cxx, I<BR>> > > > notice that the OutputImageType of filter is unsigned short, which I<BR>> > > > don't quite understand. The output should contains both negative<BR>> > > > and positive distance, why use "unsigned" here?<BR>> > > ><BR>> > > > Thanks<BR>> > > > Siqi<BR>> > > ><BR>> > > > MSN保护盾，十八般武艺保障MSN安全！ 现<BR>> > > > 在就下载！ _______________________________________________<BR>> > > > Insight-users mailing list<BR>> > > > Insight-users@itk.org<BR>> > > > http://www.itk.org/mailman/listinfo/insight-users<BR>> > ><BR>> > <BR>> > <BR>> > ------------------------------------------------------------------------<BR>> > 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><BR>> > <BR>> > <BR>> > ------------------------------------------------------------------------<BR>> > <BR>> > _______________________________________________<BR>> > Insight-users mailing list<BR>> > Insight-users@itk.org<BR>> > http://www.itk.org/mailman/listinfo/insight-users<BR><BR><br /><hr />使用新一代 Windows Live Messenger 轻松交流和共享！ <a href='http://im.live.cn/' target='_new'>立刻下载！</a></body>
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