[vtkusers] vtkImageReslice rotation and resampling question

[David Gobbi]

Hi Richard,

SetInformationInput(), not SetInformation().  The former (the one you need
to use) requires a vtkImageData as input.  It provides the reference image
that defines the geometry for the reslicing.

 - David

On Wed, Jul 20, 2016 at 7:55 AM, Richard Brown <richard.j.brown at live.co.uk>
wrote:

> Hi David,
>
> I’ve been working through your advice and I get an error:
> Attempt to get an input array for an index that has not been specified
>
> My code looks like yours:
>  vtkSmartPointer<vtkImageReslice> imageReslice = vtkSmartPointer<
> vtkImageReslice>::New();
>
>     imageReslice->SetInputData(kernelImageData);
>
>     imageReslice->SetInformation(doseGrid->GetInformation());
>
>     imageReslice->SetInterpolationModeToLinear();
>
>     imageReslice->SetResliceTransform(transform);
>
>     imageReslice->Update();
>
>
> It seems like the error is coming from doseGrid (when I comment it out,
> the error goes away). The dose grid was initialised like this:
>
>     vtkSmartPointer<vtkImageData> doseGrid = vtkSmartPointer<vtkImageData>::New();
>
>     doseGrid->SetOrigin(0.,0.,0.);
>
>     doseGrid->SetDimensions(500,500,500);
>
>     doseGrid->SetSpacing(0.5,0.5,0.5);
>
>     doseGrid->AllocateScalars(VTK_DOUBLE,1);
>
>
> Any idea what I’ve done wrong?
>
> Regards,
> Richard
>
> On 08 Jul 2016, at 17:42, David Gobbi <david.gobbi at gmail.com> wrote:
>
> Hi Richard,
>
> Yes, you can use vtkImageReslice for this.  It would work like this:
>
> Let's define T as the transform that gives the position and orientation of
> the kernel within the larger image.  To resample the kernel, you would give
> vtkImageReslice the inverse of T as the ResliceTransform, and you would
> supply the larger image as a reference image, e.g. the code would look like
> this (using Python):
>
> reslice = vtkImageReslice()
> reslice.SetInputData(kernel_image)
> reslice.SetInformationInput(big_image)
> reslice.SetResliceTransform(inverse_transform)
> reslice.SetInterpolationModeToLinear()
> reslice.Update()
>
> This will produce something like the bottom image from your original
> email. In order for the kernel resampling to work properly, your kernel
> image must have a border which is all zeros.  If this must be done over and
> over again (i.e. if you need to superimpose the kernel hundreds of times at
> various locations within the larger image) then the above procedure won't
> be fast enough. Another possibility is to use the vtkImageInterpolator
> class and some of your own ingenuity to create a fast method for resampling
> and superposing the kernel.
>
> During my PhD, I wrote a custom VTK class that superposed kernels into a
> volume in order to do 3D ultrasound reconstruction, but I never generalized
> it:
>
> https://github.com/dgobbi/AIGS/blob/master/Ultrasound/vtkFreehandUltrasound.h
>
> Some further development of this code was done for the PLUS toolkit:
>
> https://app.assembla.com/spaces/plus/subversion/source/HEAD/trunk/PlusLib/src/PlusVolumeReconstruction
>
> However, as far as I know, VTK doesn't provide an efficient
> general-purpose way of superposing kernels at different positions and
> orientations into a 3D volume.
>
>  - David
>
>
>
> On Fri, Jul 8, 2016 at 7:07 AM, Richard Brown <richard.j.brown at live.co.uk>
> wrote:
>
>>
>> Hi all,
>>
>> I have a fairly simple problem, and one that I’m sure has previously been
>> solved here, but I’m struggling to find the right keywords to find a useful
>> thread.
>>
>> I would like to superpose a kernel vtkImageData (kernel.png) onto a grid
>> vtkImageData (grid.png). The kernel will be rotated (superpose.png),
>> however, so the kernel will requiring resampling before superposition is
>> possible (superposition_and_resample.png).
>>
>> What is the best way to do this? I feel like I can simply use
>> vtkImageReslice, but I’m not 100%.
>>
>> Thanks in advance for any pointers.
>>
>> Regards,
>> Richard
>>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/vtkusers/attachments/20160720/e776f4d0/attachment.html>