[vtkusers] test if vtkImageData is blank

[David Gobbi]

Hi Jonathan,

You have to go one level deeper with the Modified() call.
Here is the recipe, both modified calls are necessary:

image.Modified()
image.GetPointData().GetScalars().Modified()
range = image.GetScalarRange()

This is because both vtkImageData and vtkDataArray have
their own timestamps.

 - David



On Sun, Dec 26, 2010 at 12:08 PM, Jonathan Morra <jonmorra at gmail.com> wrote:
> I tried this, and after invoking Modified() on the image data, the scalar
> range is still [0, 0].
>
> On Sun, Dec 26, 2010 at 10:15 AM, Karthik Krishnan
> <karthik.krishnan at kitware.com> wrote:
>>
>> GetScalarRange will re-compute the scalar range only if the image has been
>> modified. It has time stamps internally to avoid re-computing the scalar
>> range during every call to GetScalarRange().
>>
>> The method SetScalarComponentFromDouble does not change the MTime of the
>> image for efficiency.
>>
>> Invoke Modified() on the image and then invoke GetScalarRange() and you
>> should see it update.
>>
>>
>> --
>> karthik
>>
>>
>>
>> On Sun, Dec 26, 2010 at 11:19 PM, Sebastien Jourdain
>> <sebastien.jourdain at kitware.com> wrote:
>>>
>>> I have no idea on the expected behavior... And I'm not much familiar
>>> with imageData...
>>>
>>> Sorry,
>>>
>>> Seb
>>>
>>> On Sun, Dec 26, 2010 at 6:27 PM, Jonathan Morra <jonmorra at gmail.com>
>>> wrote:
>>> > This would appear to work, but after
>>> > calling .SetScalarComponentFromDouble(x, y, z, 0, 1) the
>>> > image.GetScalarRange() still returns [0, 0] which, I would assume, it
>>> > shouldn't.  Am I doing something wrong?
>>> >
>>> > On Sun, Dec 26, 2010 at 8:47 AM, Sebastien Jourdain
>>> > <sebastien.jourdain at kitware.com> wrote:
>>> >>
>>> >> If you have a scalar range on the data array and if the min/max are
>>> >> equal to 0, you are done...
>>> >>
>>> >> Seb
>>> >>
>>> >> On Mon, Dec 20, 2010 at 6:15 PM, Jonathan Morra <jonmorra at gmail.com>
>>> >> wrote:
>>> >> > Is there a way to quickly tell if a vtkImageData is blank (contains
>>> >> > all
>>> >> > 0's)?  I can't iterate the pixels cause I'm in Java and that's too
>>> >> > slow.
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>
>
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