[vtkusers] Access to Cells in VTK.js

Sebastien Jourdain sebastien.jourdain at kitware.com
Thu Jan 17 15:49:29 EST 2019

You can do that by calling getPoint(idx) on the image data based on it's

idx = i + j * dims[0] + k * dims[0] * dims[1]

for the ijk of the points. You can easily convert from the ijk of a cell to
the ijk of the point. based on which corner you want.



On Thu, Jan 17, 2019 at 11:56 AM Andrzej Marciniak <
marciniak.andrzej.zg at gmail.com> wrote:

> Hi All,
> My question is: for a given IJK data cell position in vtkImageData, how can
> I get access to:
> - voxel value,
> - voxel bounds (position of all 8 vertices of a voxel)
> - all voxels belonging to a given vtkImageSlice.
> More detailed description of why I need this:
> I am working on a tool for annotations and segmentations of MRI images
> using
> vtk.js with vtkImageData to represent MRI volume. I tried to use
> vtkImageSlice for both original image (grayscale) and overlay (color), but
> since there is no transparency for background voxels in vtkImageSlice (i.e.
> there is opacity property but no alpha), I had to use a different
> approach.
> Now, I am using "my own" transparent canvas as segmentation/annotation
> layer
> and vtkImageSlice to represent original image.
> To establish position of annotation I use picker. Using
> - picker.getPickedPositions()[0]
> - picker.getCellIJK()
> I can get both world position and cell position for a picked point. This
> works great, including interactions like zooming, pan, windowlevel, slicing
> etc. (see picture).
> <http://vtk.1045678.n5.nabble.com/file/t342677/annotationTool.png>
> However, I would like to draw on my canvas not only points (as in the
> picture), but also full rectangles covering voxels. To do that I need to
> know position of 4 vertices of voxel in a given plane and its value (I want
> to mark it with different color regarding the value).
> Thanks
> Andrzej
> --
> Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
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