[vtkusers] vtkImageReader and actual file access time

[Hamid]

Hi

I am a complete newbie when it comes to streaming and caching data to save  
memory.
So I was wondering if anybody could tell me when VTK exactly does the file  
reading and accesses the file from hard disk.
Does it do piece by piece or it reads the whole image file and keeps it in  
cache ?

Say, I have this code:

	vtkBMPReader *reader = vtkBMPReader::New();
	vtkImageData *data = vtkImageData::New();
	vtkImageViewer *viewer = vtkImageViewer::New();

	reader->SetDataSpacing(1.0,1.0,2.0);
	reader->SetDataOrigin(0.0,0.0,0.0);
	reader->SetFileName("image.bmp");

	viewer->SetInput(reader->GetOutput());
	viewer->SetColorWindow(255);
	viewer->SetColorLevel(127.5);
	viewer->Render();

The actual reading off the hard disk happens when it hits the  
reader->GetOutput() or viewer->Render() ?

Any input is appreciated
Thanks
Hamid

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