[vtkusers] problem with vtkvolume16reader->GetOutput()->GetScalarPointer()??

[Dumont Nicolas]

Hello users!!

I wish to make a copy of my volume data in a new vtkimagedata object, so
after that i could modify the scalar data at the voxels (for example to
make a spherical hole inside the volume).

The code I wrote works well with

vtkPNGreader->GetOutput()->GetScalarPointer();

but the same code adapted for

vtkVolume16reader->GetOutput()->GetScalarPointer();

returns me the error that GetScalarPointer() points to memory 0x0000000000
and so cant be read.

Any body has an idea why it is so ?

Nicolas D.
Ulg, Belgium



Here are both pieces of code:

****************************************************
vtkPNGReader * reader = vtkPNGReader::New();
	reader->SetFilePattern("MR/%d.png");
	reader->SetDataExtent(1,256,1,256,0,126);
	reader->SetDataSpacing(1,1,1.5);
	reader->SetDataOrigin(0,0,0);
	reader->UpdateWholeExtent();


vtkImageData *imageData = vtkImageData::New();
	imageData->SetDimensions(256,256,126);
	imageData->SetSpacing(1,1,1.5);
	imageData->SetOrigin(0.0,0.0,0.0);
	imageData->SetScalarTypeToUnsignedChar();
	imageData->SetNumberOfScalarComponents(1);
	imageData->AllocateScalars();
	imageData->GetPointData()->CopyScalarsOn();

unsigned char *ptrReader =
(unsigned char *) reader->GetOutput()->GetScalarPointer();
unsigned char *ptrData =
(unsigned char *) imageData->GetScalarPointer();

for (int i=0; i<256*256*126; i++)
{
	*ptrData = *ptrReader;
	ptrData++;
	ptrReader++;
}

//...
    volumeMapper->SetInput(imageData);
//...

***********************************************************************
vtkVolume16Reader *v16 = vtkVolume16Reader::New();
    v16->SetDataDimensions(64,64);
    v16->SetDataByteOrderToLittleEndian();
    v16->SetFilePrefix ("quarter");
    v16->SetImageRange(1, 93);
    v16->SetDataSpacing (3.2, 3.2, 1.5);

vtkImageData *imageData = vtkImageData::New();
	imageData->SetDimensions(64,64,93);
	imageData->SetSpacing(3.2,3.2,1.5);
	imageData->SetOrigin(0.0,0.0,0.0);
	imageData->SetScalarTypeToUnsignedChar();
	imageData->SetNumberOfScalarComponents(1);
	imageData->AllocateScalars();
	imageData->GetPointData()->CopyScalarsOn();

unsigned char *ptr2 =
(unsigned char *) v16->GetOutput()->GetScalarPointer();
unsigned char *ptr =
(unsigned char *) imageData->GetScalarPointer();

for (int i=0; i<64*64*93; i++)
{
	*ptr = *ptr2;
	ptr++;
	ptr2++;
}
//...
    volumeMapper->SetInput(imageData);
//...