Extrakt zero crossings from an image.

zero_crossing returns the zero crossings of the input image as a region. A pixel is accepted as a zero crossing if its gray value (in Image) is zero, or if at least one of its neighbors of the 4-neighborhood has a different sign.

This operator is intended to be used after edge operators returning the second derivative of the image (e.g., laplace_of_gauss), which were possibly followed by a smoothing operator. In this case, the zero crossings are (candidates for) edges.

zero_crossing usually returns the value 2 (H_MSG_TRUE). If necessary, an exception is raised.

zero_crossing is reentrant and automatically parallelized (on tuple level).

laplace, laplace_of_gauss, derivate_gauss

connection, skeleton, boundary, select_shape, fill_up

threshold, dual_threshold, zero_crossing_sub_pix

Foundation