Ghosts and Extents (was [vtkusers] vtkImageImport in java?)

[Stewart, Terry]

Steve,

  I'm using Java and ran into a similar situation while trying to get my
internally-generated RGB image into vtkImageData.  I'd tried the
vtkImageImport path too only to run into the same roadblock with the
missing [Copy|Set]ImportVoidPointer() methods for Java.  I've gotten my
logic to a functional state via:

   vtkImageData imageData = new vtkImageData();
         :
   for (x = 0; ...)
      for (y = 0; ... )
         imageData.SetScalarComponentFromDouble(x, y, 0, rComp, (double)
buffer[byteIndex++]);
         imageData.SetScalarComponentFromDouble(x, y, 0, gComp, (double)
buffer[byteIndex++]);
         imageData.SetScalarComponentFromDouble(x, y, 0, bComp, (double)
buffer[byteIndex++]); 

However this is quite slow.  Did you use some other mechanism to get
your image data inserted into vtkImageData that is perhaps more
efficient?  

Thx.

Terry

>Howdy,
>
>On Fri, Jan 28, 2005 at 03:25:44PM -0500, Steve M. Robbins wrote:
>
>> Has anyone got example code that builds image data from 
>scratch in Java?
>> Ultimately I'd like a vtkImageData object.
>> 
>> I considered using vtkImageImport in java but there doesn't 
>appear to 
>> be any access to the two methods that actually copy data:
>> CopyImportVoidPointer() and SetImportVoidPointer().  :-/
>
>I went back to copying the data directly into a vtkImageData 
>object and finally managed to get things working.  It turns 
>out that the only bit that I had missed initially was to call 
>SetWholeExtent().  Using just SetExtent() is not enough, it seems.
>
>
>I have read the VTK User's Guide.  The chapter on how the 
>pipeline operates is helpful, but I'm still not sure exactly 
>what is the distinction between "extent", "whole extent" and 
>"update extent".  I get the feeling that the update extent is 
>set at the output end of the pipeline (e.g. by mappers) and 
>propagated backwards towards the source objects, but even that 
>is not clear.  Who is responsible for setting the other two 
>extents?  And what is a "ghost level"?
>
>Is there any documentation that defines these terms?
>
>How about source code: is there a particularly good class to 
>start with?  Data class?  Source class?  Reader?
>
>Thanks,
>-Steve
>
>