itk filereader causes access violation exception

Question

I have a problem with an Access Violation Exception. I am using itk and read a File with it's file reader.

ThreeDImageFloatType* MyClass::loadImage(std::string filename){
const char* cfilename = filename.c_str();
fileReader = ImageFileReaderType::New();
fileReader->SetFileName(cfilename);

try{ 
    fileReader->Update();
}catch( ... ) {
    std::cerr << "failed to read file " << filename << std::endl; 
}

CastFilterType::Pointer castFilter = CastFilterType::New();
castFilter->SetInput(fileReader->GetOutput());


castFilter->Update();

//ThreeDImageFloatType *t3dim = castFilter->GetOutput();
t3dim = castFilter->GetOutput();
return t3dim;
}

This is a function the class also contains 2 global variables:

ImageFileReaderType::Pointer fileReader;
ThreeDImageFloatType *t3dim;

Now if you call the the function in the class from for example my main method and try to access the return value, something like t3dim->GetLargestPossibleRegion().GetSize();. I get an access violation error. It is important to notice if i don't outsource the code, and have it within the main method, it works like a charm. What could be the problem? How do i fix that?

[edit] I tried replacing the string filename with a const char* filename. The main method looks like this.

MyClass imIO;

const char* filename = "path to file";
ThreeDImageFloatType *t3dim = imIO.loadImage(filename);
t3dim->GetLargestPossibleRegion().GetSize();

Again if i put the code from the function completly in the main method it works.

[/edit]

[offtopic] maybe a moderator can tag it as itk, since it is an itk specific question? [/offtopic]

ITK - itk.org - ITK is an open-source, cross-platform system that provides developers with an extensive suite of software tools for image analysis. — Mike Clark
Of course you know what ITK is, but other people will not know what it is. I did not know. I put the link there so that other people could more easily find out what it is, and read its documentation if they liked. — Mike Clark

scigor scigor · Accepted Answer · 2010-10-31T22:37:33

I just found the answer myself. The Solution to the Problem lies within this line:

fileReader = ImageFileReaderType::New();

It's a smart pointer. So when the function returns, it gets unregistered. So the pointer received from that function to an internal buffer (the read file), can't be used any more. While the pointer points to actual memory, it can't be accessed any more. Access Violation Error.

itk filereader causes access violation exception

2 Answers