[vtkusers] displaying histogram using vtkImageAccumulate

[Prathamesh Kulkarni]

Thanks for the pointer to the example.

As the example says:

"It appears the maximum frequency of a histogram generated by
vtkImageAccumulate, when that frequency corresponds to the value of 0,
cannot be disabled by setting ignore zero to true! See lines 245 and 218 in
vtkImageAccumulate.cxx "

However, just in case, this can be bypassed by setting (for a 1D histogram):

histogram->SetComponentExtent(1, x_max, 0, 0, 0, 0); instead of
histogram->SetComponentExtent(0, x_max, 0, 0, 0, 0);


Prathamesh

On Tue, Jul 20, 2010 at 10:50 AM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Prathamesh,
>
> The output of vtkImageAccumulate must be plotted in order to show the
> histogram:
> http://www.vtk.org/Wiki/VTK/Examples/Images/HistogramXYPlot
>
>  David
>
>
>
> On Tue, Jul 20, 2010 at 8:44 AM, Prathamesh Kulkarni
> <prathameshmkulkarni at gmail.com> wrote:
> >
> > Hello all,
> >
> > I want to be able to display histogram of a part of an image. Following
> is
> > what I did so far:
> >
> > image_accumulate->SetInput(vtkImageData);
> > image_accumulate->SetStencil(vtkImageStencilData);
> > image_accumulate->Update();
> >
> > histogram_image = image_accumulate->GetOutput();
> > histogram_image->Update();
> >
> >
> > When I cast the histogram image to unsigned char and render it using
> > vtkImageActor, I see a blank white image. Am I missing something here?
> >
> >
> > Thanks,
> > Prathamesh
> >
> >
> >
> >
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