[vtkusers] Faster way to create a vtkImageData with a single value

[Sujin Philip]

Hi,

A much faster way would be to replace the for loop with this:
imgvtk.GetPointData().GetScalars().Filll(background_value)

-Sujin


On Sun, Jan 29, 2017 at 2:37 PM, jmerkow <jmerkow at gmail.com> wrote:

> Hello,
>
> I am working in creating volume images from PolyData using
> vtkPolyDataToImageStencil and vtkImageStencil.
> The process is outline here:[1] (for 2D images).
> To do this, you need to fill a vtkImageData with a background (or
> foreground) value.
> Something like this:
>
>     imgvtk = vtk.vtkImageData()
>     imgvtk.SetSpacing(spacing)
>     imgvtk.SetOrigin(origin)
>     imgvtk.SetExtent(extent)
>     imgvtk.AllocateScalars(vtk.VTK_UNSIGNED_CHAR, 1)
>
>     # fill vtk image with background
>     count = imgvtk.GetNumberOfPoints()
>     for i in range(count):
>         imgvtk.GetPointData().GetScalars().SetTuple1(i, backgroud_value);
>
>
> However, this is very very slow, by far the slowest part of the process.
> Is
> there a faster way to do this?
>
>
> Full code:
> import vtk
> from vtk.util import numpy_support
>
> def pd_to_numpy_vol(pd, spacing=[1.,1.,1.], shape=None, origin=None
> foreground_value=255, backgroud_value = 0):
>     if shape is None:
>         bnds = np.array(pd.GetBounds())
>         shape = np.ceil((bnds[1::2]-bnds[::2])/spacing).astype(int)+15
>     if origin is None:
>         origin = bnds[::2]+(bnds[1::2]-bnds[::2])/2
>
>     #make image
>     extent = np.zeros(6).astype(int)
>     extent[1::2] = np.array(shape)-1
>     imgvtk = vtk.vtkImageData()
>     imgvtk.SetSpacing(spacing)
>     imgvtk.SetOrigin(origin)
>     imgvtk.SetExtent(extent)
>     imgvtk.AllocateScalars(vtk.VTK_UNSIGNED_CHAR, 1)
>
>     # fill vtk image with background
>     count = imgvtk.GetNumberOfPoints()
>     for i in range(count):
>         imgvtk.GetPointData().GetScalars().SetTuple1(i, backgroud_value);
>
>     #poly2 stencil
>     pol2stenc = vtk.vtkPolyDataToImageStencil()
>     pol2stenc.SetInputData(pd)
>     pol2stenc.SetOutputSpacing(spacing)
>     pol2stenc.SetOutputOrigin(origin)
>     pol2stenc.SetOutputWholeExtent(extent)
>     pol2stenc.Update()
>
>     #stencil to image
>     imgstenc = vtk.vtkImageStencil()
>     imgstenc.SetInputData(imgvtk)
>     imgstenc.SetStencilConnection(pol2stenc.GetOutputPort())
>     imgstenc.ReverseStencilOn()
>     imgstenc.SetBackgroundValue(foreground_value)
>     imgstenc.Update()
>
>     ndseg =
> numpy_support.vtk_to_numpy(imgstenc.GetOutputDataObject(
> 0).GetPointData().GetArray(0))
>     return ndseg.reshape(sitk.GetArrayFromImage(seg).shape)
>
>
>
>
>
>
>
>
> --
> View this message in context: http://vtk.1045678.n5.nabble.
> com/Faster-way-to-create-a-vtkImageData-with-a-single-value-tp5741978.html
> Sent from the VTK - Users mailing list archive at Nabble.com.
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