[vtkusers] Rotating image data

Mon Jul 12 08:48:55 EDT 2010

in your hybrid approach you said that yiou use vtkImageReslice for operations
that require a regridding of the image (e.g. extracting oblique
slices) and use either vtkImageReslice or the camera for doing
operations like pan and zoom.

a couple of questions:
1- when you said regridding (extracting oblique slices), do you
include special cases of obliqueness: saggital, coronal and axial?
2- "and use either vtkImageReslice or the camera": what are the
situation for using vtkImageReslice or the camera.
3- what do you think of these pipelines:

    For simply viewing axial slices, change between them, etc:
        vtkGDCMImageReader -> vtkImageMapToWindowLevelColors2 ->
vtkImageActor -> vtkRenderer -> vtkRenderWindow

    For extracting oblique slices (sagittal, coronal, axial, obliques)
and change between them, something like an MPR view:
        vtkGDCMImageReader ->vtkImageReslice ->
vtkImageMapToWindowLevelColors2 -> vtkImageActor -> vtkRenderer ->
vtkRenderWindow

On Fri, Jul 9, 2010 at 12:48 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> All operations by vtkImageReslice are done on the CPU.  Around 80% of
> the code in vtkImageReslice consists of special-case optimizations,
> and it is quite efficient for a CPU-based interpolator, but is still
> purely CPU and not GPU.
>
> I use a hybrid approach where I use vtkImageReslice for operations
> that require a regridding of the image (e.g. extracting oblique
> slices) and use either vtkImageReslice or the camera for doing
> operations like pan and zoom, according to a complex set of rules that
> determine what to do according to the chosen quality/speed tradeoff.
>
> More-or-less, the only thing that matters in terms of getting the
> correct visual result is the coordinate transformation between pixels
> on your screen and the voxels in your image.  The basic image display
> pipeline should consist of vtkImageReslice, vtkImageActor, and then
> the Camera/Renderer/RenderWindow.  By understanding the coordinate
> transformation that occurs at each stage, you can change which part of
> the pipeline does what in order to get the best efficiency.
>
>   David
>
>
>
>
> On Fri, Jul 9, 2010 at 10:28 AM, Lic. José M. Rodriguez Bacallao
> <jmrbcu at gmail.com> wrote:
>> does all operation performed by vtkImageReslice are costly?
>> I don't remember where, but in some book I did read that I should
>> never modify the pixel matrix (some vtk book), just the camera but as
>> I see, you did modify the camera, is this ok, why?
>>
>> On Fri, Jul 9, 2010 at 10:31 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> I'd better add an errata to what I wrote:
>>>
>>> 3) Each (x,y,z) point is transformed by the ResliceAxes matrix, and
>>> then the ResliceTransform, in that order.
>>>
>>> I had the two operations reversed.
>>>
>>>   David
>>>
>>>
>>> On Fri, Jul 9, 2010 at 8:21 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>> Really, vtkImageReslice is the only straightforward way to rotate an
>>>> image in VTK.  It does change the pixel matrix, the basic job of
>>>> ImageReslice is to resample an image through a transform.
>>>>
>>>> The operation of vtkImageReslice is like so:
>>>> 1) The output Extent/Origin/Spacing of vtkImageReslice define an
>>>> output voxel grid.
>>>> 2) Reslice loops through all output voxels, and computes the (x,y,z)
>>>> data coords for each voxel in turn.
>>>> 3) Each (x,y,z) point is transformed by the ResliceTransform, and then
>>>> the ResliceAxes matrix, in that order.
>>>> 4) The reslice's input data is interpolated at the transformed (x',y',z') point.
>>>> 5) The interpolated value from the input at coordinate (x',y',z') is
>>>> used to set the value of the output voxel at (x,y,z).
>>>>
>>>> Lots of people have trouble with (1).  Because vtkImageReslice isn't a
>>>> vtkProp it doesn't know anything about how it's output will be
>>>> displayed, it doesn't know how to properly set its own output voxel
>>>> grid.  So you should usually set the output Spacing/Origin/Extent
>>>> manually.  If you don't, then vtkImageReslice will try to "guess" what
>>>> a reasonable output grid would be, and it will usually guess wrong,
>>>> because it doesn't know anything about how the image will eventually
>>>> be displayed.
>>>>
>>>> I've had a plan for a long time now to write a vtkProp3D based around
>>>> vtkImageReslice that will do all the mathematical trickery needed to
>>>> make VTK more friendly for 3D image display.  In my own image display
>>>> applications, I set up some low-level observers that keep track of the
>>>> camera position and the window size, and then have those observers set
>>>> the vtkImageReslice parameters so that the image displays exactly the
>>>> way that it should.
>>>>
>>>>   David
>>>>
>>>>
>>>>
>>>>
>>>> On Fri, Jul 9, 2010 at 7:52 AM, Lic. José M. Rodriguez Bacallao
>>>> <jmrbcu at gmail.com> wrote:
>>>>> this may be a silly question:
>>>>> 1- which is the correct preffered way to rotate(transform) an image,
>>>>> with the camera or with vtkImageReslice?
>>>>> 2- does vtkImageReslice change/transform the pixel matrix?
>>>>>
>>>>>
>>>>> On Fri, Jul 9, 2010 at 7:34 AM, Jothy <jothybasu at gmail.com> wrote:
>>>>>> Some sort of padding befor rotation should help.
>>>>>>
>>>>>> Jothy
>>>>>>
>>>>>> On Fri, Jul 9, 2010 at 12:32 PM, Srinivasa Rao <srinivas at rsageventures.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> Hi All,
>>>>>>>    I am trying to rotate vtkImageData using vtkTransform and
>>>>>>> vtkImageReslice, i used following code to do the job.
>>>>>>>
>>>>>>> vtkImageData * rotateImage(vtkImageData *data, QPointF center, int angle)
>>>>>>> {
>>>>>>>         vtkTransform *imageTransform = vtkTransform::New();
>>>>>>>         imageTransform->PostMultiply();
>>>>>>>         imageTransform->Translate(center.x(), center.y(), 0.0);
>>>>>>>         imageTransform->RotateZ(angle);
>>>>>>>        imageTransform->Translate(-center.x(), -center.y(), 0.0);
>>>>>>>         // Now create filter and set previously created transformation
>>>>>>>         vtkImageReslice *algo = vtkImageReslice::New();
>>>>>>>         algo->SetInput(data);
>>>>>>>         algo->SetInformationInput(data);
>>>>>>>         algo->SetResliceTransform(imageTransform);
>>>>>>>         algo->SetInterpolationModeToLinear();
>>>>>>>         algo->Update();
>>>>>>>         return algo->GetOutput();
>>>>>>> }
>>>>>>>
>>>>>>> When i try to rotate image data, after rotation the data which is outside
>>>>>>> the image is getting lost.
>>>>>>> Is there a way around to rotate image data without data loss..
>>>>>>> thanks in advance.
>>>>>>> regards,
>>>>>>> srinivas.
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>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Powered by www.kitware.com
>>>>>>
>>>>>> Visit other Kitware open-source projects at
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>>>>>>
>>>>>> Please keep messages on-topic and check the VTK FAQ at:
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>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Lic. José M. Rodriguez Bacallao
>>>>> Centro de Biofisica Medica
>>>>> -----------------------------------------------------------------
>>>>> Todos somos muy ignorantes, lo que ocurre es que no todos ignoramos lo mismo.
>>>>>
>>>>> Recuerda: El arca de Noe fue construida por aficionados, el titanic
>>>>> por profesionales
>>>>> -----------------------------------------------------------------
>>>>> _______________________________________________
>>>>> Powered by www.kitware.com
>>>>>
>>>>> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>>>>>
>>>>> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>>>>>
>>>>> Follow this link to subscribe/unsubscribe:
>>>>> http://www.vtk.org/mailman/listinfo/vtkusers
>>>>>
>>>>
>>>
>>
>>
>>
>> --
>> Lic. José M. Rodriguez Bacallao
>> Centro de Biofisica Medica
>> -----------------------------------------------------------------
>> Todos somos muy ignorantes, lo que ocurre es que no todos ignoramos lo mismo.
>>
>> Recuerda: El arca de Noe fue construida por aficionados, el titanic
>> por profesionales
>> -----------------------------------------------------------------
>>
>

-- 
Lic. José M. Rodriguez Bacallao
Centro de Biofisica Medica
-----------------------------------------------------------------
Todos somos muy ignorantes, lo que ocurre es que no todos ignoramos lo mismo.

Recuerda: El arca de Noe fue construida por aficionados, el titanic
por profesionales
-----------------------------------------------------------------