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# scipy.ndimage.morphology.binary_propagation

`scipy.ndimage.morphology.``binary_propagation`(input, structure=None, mask=None, output=None, border_value=0, origin=0)

  Multi-dimensional binary propagation with the given structuring element.

  Parameters : | input : array_like Binary image to be propagated inside mask. structure : array_like Structuring element used in the successive dilations. The output may depend on the structuring element, especially if mask has several connex components. If no structuring element is provided, an element is generated with a squared connectivity equal to one. mask : array_like Binary mask defining the region into which input is allowed to propagate. output : ndarray, optional Array of the same shape as input, into which the output is placed. By default, a new array is created. origin : int or tuple of ints, optional Placement of the filter, by default 0.
  Returns : | ouput : ndarray Binary propagation of input inside mask.

  Notes

  This function is functionally equivalent to calling binary_dilation with the number of iterations less then one: iterative dilation until the result does not change anymore.

  The succession of an erosion and propagation inside the original image can be used instead of an opening for deleting small objects while keeping the contours of larger objects untouched.

  References

  [R61] | http://cmm.ensmp.fr/~serra/cours/pdf/en/ch6en.pdf, slide 15.

  [R62] | http://www.qi.tnw.tudelft.nl/Courses/FIP/noframes/fip-Morpholo.html#Heading102

  Examples

      >>> input = np.zeros((8, 8), dtype=np.int)
      >>> input[2, 2] = 1
      >>> mask = np.zeros((8, 8), dtype=np.int)
      >>> mask[1:4, 1:4] = mask[4, 4]  = mask[6:8, 6:8] = 1
      >>> input
      array([[0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 1, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0]])
      >>> mask
      array([[0, 0, 0, 0, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 0, 0, 0, 1, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 1, 1],
             [0, 0, 0, 0, 0, 0, 1, 1]])
      >>> ndimage.binary_propagation(input, mask=mask).astype(np.int)
      array([[0, 0, 0, 0, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0]])
      >>> ndimage.binary_propagation(input, mask=mask,\
      ... structure=np.ones((3,3))).astype(np.int)
      array([[0, 0, 0, 0, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 1, 1, 1, 0, 0, 0, 0],
             [0, 0, 0, 0, 1, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0, 0, 0]])

      >>> # Comparison between opening and erosion+propagation
      >>> a = np.zeros((6,6), dtype=np.int)
      >>> a[2:5, 2:5] = 1; a[0, 0] = 1; a[5, 5] = 1
      >>> a
      array([[1, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 0, 0, 0, 1]])
      >>> ndimage.binary_opening(a).astype(np.int)
      array([[0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0],
             [0, 0, 0, 1, 0, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 0, 1, 0, 0],
             [0, 0, 0, 0, 0, 0]])
      >>> b = ndimage.binary_erosion(a)
      >>> b.astype(int)
      array([[0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0],
             [0, 0, 0, 1, 0, 0],
             [0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0]])
      >>> ndimage.binary_propagation(b, mask=a).astype(np.int)
      array([[0, 0, 0, 0, 0, 0],
             [0, 0, 0, 0, 0, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 1, 1, 1, 0],
             [0, 0, 0, 0, 0, 0]])

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