[vtk-developers] VTK-Python: Numeric Array <-> ImageData.

[Prabhu Ramachandran]

hi,

Just committed some new and old code to VTK CVS and I need some help.

I've added the following to Wrapping/Python/vtk/util/

 vtkConstants.py, vtkImageExportToArray.py and
 vtkImageImportFromArray.py

These files were originally in VTK 3.2 and written by David Gobbi.
I've updated them to VTK 4.x.  That required a few lines of change
here and there.  I did however test it quite a bit to my limited
knowledge.

I've also added a test for the vtkImage*Array.py code here:

 Imaging/Testing/Python/TestNumericArrayImageData.py

Run it like so:

vtkpython TestNumericArrayImageData.py -B $VTK_DATA_ROOT/Baseline/Imaging

It tests the code by first exporting a PNG image to a Numeric Array
and then converts the array to an image and compares that image to the
original image.  It does this for all PNG images in a particular
directory.  So AFAIK it is fairly rigorous since it passes (zero
threshold) on all the images in Baseline/Imaging.  Takes a while
though (~7 secs on a PIII 450).

I have not setup the Testing/Python directory to include the tests in
the nightly regression tests because I have a couple of questions.

 1. The test obviously requires Numeric to be installed.  Right now I
 fail the test if Numeric is not installed (I print a message saying
 Numeric is necessary).  Is this OK or should I pass the test (ugh!)
 and print the message alone?  I really would appreciate advice on
 this.  I think most folks using VTK-Python will use Numeric so its
 not too much to ask for a Numeric install.  However do all the
 machines that test VTK-Python have Numeric installed?

 2. While testing the code I ran into problems with vtkPNGReader.  I
 was doing something like this:

  reader = vtk.vtkPNGReader()
  for i in bunch_of_png_images:
      reader.SetFileName(i)
      reader.Update()
      # use reader.GetOutput()

 And I had lots of trouble with this.  Basically after a few tests
 passing it would segfault!  I fixed the error by simply instatiating
 the vtkPNGReader each time inside the loop.  So unless I don't know
 something about the reader this is a bug.  I looked at the
 vtkImageReader2.cxx code for SetFileName and it seems to read ok.
 Anyone have clues on this?

I'd very much appreciate comments.  If my first question is cleared up
I can make it so that the nightly tests run this test also.

David, are the tests adequate?  I don't know enough about the imaging
pipeline to do a good enough job but I guess the present test is a
start.  Feel free to add more. :)

Thanks,
prabhu