[vtkusers] Can anyone help on how to extract grey/color information from image pixel by pixel in VTK?

[Q Ma]

Hi, there,

I used vtkJPEGReader to read in a JPG image.
Then, I try to extract grey/color information from image pixel by pixel.
Although some methods seem should work, such as:
vtkJPEGReader->GetOutput()->GetScalarComponentAsFloat(x,y,z,0)
However, I can not make it work.

Can anyone give me some idea on how to do this?
Thanks.

Regards,
Qi