[vtkusers] Image from OpenCV as texture

Addison Elliott

2018-10-28 18:30:51 UTC

I came across a similar problem when I was working on a VTK application in
Python. There are few examples of how to do this (if any).

Take a look at this excerpt of code that I use to load in RGB data. In
short, the answer to your problem is to have the data is NxM where N is the
product of the size of the data (i.e. 10x10x10 => N = 1000) and M is the
number of color channels you have (1 for grayscale, 3 for RGB, 4 for RGBA).

# Use VTK support function to convert Numpy to VTK array
# The data is reshaped to one long 2D array where the first dimension is
the data and the second dimension is
# the color channels (1, 3 or 4 typically)
# Note: Fortran memory ordering is required to import the data correctly
# Type is not specified, default is to use type of Numpy array
vtkArray = numpy_support.numpy_to_vtk(self.data.reshape((-1,
self.channels), order='F'), deep=False)

# Create image, set parameters and import data
self.vtkImage = vtkImageData()

# For vtkImage, dimensions, spacing and origin is assumed to be 3D. VTK
images cannot be larger than 3D and if
# they are less than 3D, the remaining dimensions should be set to default
values. The function padRightMinimum
# adds default values to make the list 3D.
self.vtkImage.SetDimensions(padRightMinimum(self.size, 3, 1))
self.vtkImage.SetSpacing(padRightMinimum(self.spacing, 3, 1))
self.vtkImage.SetOrigin(padRightMinimum(self.origin, 3, 0))

# Import the data (vtkArray) into the vtkImage
self.vtkImage.GetPointData().SetScalars(vtkArray)

Post by Andreas Pedroni
Dear list
My final goal is to render a movie (read by the openCV method

VideoCapture) on a plane in 3D space (using VTK).

Post by Andreas Pedroni
As a first step I tried to map a single RGB-frame (a numpy nd.array

(1020, 720,3) ) as texture on a plane (see the code snippet below).

Post by Andreas Pedroni
However this does not work. What I donât get is how to create a 2D color

image to map to the texture. Now it is recognized as a 3D texture map and
returns the error: "3D texture maps currently are not supported!â.

Post by Andreas Pedroni
As I am very new to VTK and do not know anything about C++, I find it

difficult to orient myself in VTK through the C++ examples.

Post by Andreas Pedroni
So, any hints would be greatly appreciated!
Best
Andreas
# Python 3.6, VTK 8.1.1, OpenCV 3.4.2)
# Create a video capture object to read videos
cap = cv2.VideoCapture(VIDEOPATH)
# Read first frame
success, frame = cap.read()
frame_shape = frame.shape
vtk_array = numpy_support.numpy_to_vtk(frame.transpose(2, 0, 1).ravel(),

deep=True, array_type=vtk.VTK_UNSIGNED_CHAR)

Post by Andreas Pedroni
# Convert vtkFloatArray to vtkImageData
vtk_image_data = vtk.vtkImageData()
vtk_image_data.SetDimensions(frame.shape)
vtk_image_data.SetSpacing([1,1,1])
vtk_image_data.GetPointData().SetScalars(vtk_array)
vtk_image_data.SetOrigin(0,0,0)
# create the texture
atext = vtk.vtkTexture()
atext.SetInputData(vtk_image_data)
atext.InterpolateOn()
plane = vtk.vtkPlaneSource()
âŠ
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at

http://www.kitware.com/opensource/opensource.html
http://www.vtk.org/Wiki/VTK_FAQ

Post by Andreas Pedroni
Search the list archives at: http://markmail.org/search/?q=vtkusers
https://public.kitware.com/mailman/listinfo/vtkusers