CrossingDetect

CrossingDetect[image]

gives a binary image in which white pixels correspond to the zero crossings in image.

CrossingDetect[image,delta]

treats values in image that are smaller in absolute value than delta as zero.

CrossingDetect[array,…]

gives a binary sparse array in which 1 corresponds to zero crossings in array.

Details and Options

  • CrossingDetect finds pixels with positive values that have at least one negative neighbor.
  • CrossingDetect is typically used in edge-detection algorithms based on second derivatives.
  • CrossingDetect will only find zero crossings when applied to images of a real type.
  • For color images, CrossingDetect operates on the intensity averaged over all channels.
  • CrossingDetect works with 3D as well as 2D images, and also with arrays of rank 1, 2, or 3.
  • CrossingDetect takes a CornerNeighbors option. The default setting is CornerNeighbors->True.
  • Using the option setting CornerNeighbors->None, CrossingDetect operates on the dual grid whose pixels correspond to the corners in the original image, thereby reducing the dimensions of the resulting image by one pixel.

Examples

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Basic Examples  (2)

Zero crossings of a list:

Find a contour line in an elevation raster:

Scope  (1)

Find zero crossings of a 2D matrix:

Options  (2)

CornerNeighbors  (2)

Compute the crossing detect using 4- or 8-connectivity:

This operates on the dual grid:

Applications  (2)

Improved edge detection using the product of zero crossings and the first derivative of an image:

Detect edges by finding zero crossings in a second derivative image:

Properties & Relations  (2)

When computing zero crossing of data arrays, a binary SparseArray is returned:

Use Normal to expand the result:

The zero crossings of a LoG filtered image are closed contours:

Possible Issues  (1)

All data dimensions should be greater than 1 to construct the dual grid using CornerNeighbors->None:

Use CornerNeighborsAutomatic instead:

Wolfram Research (2010), CrossingDetect, Wolfram Language function, https://reference.wolfram.com/language/ref/CrossingDetect.html (updated 2014).

Text

Wolfram Research (2010), CrossingDetect, Wolfram Language function, https://reference.wolfram.com/language/ref/CrossingDetect.html (updated 2014).

CMS

Wolfram Language. 2010. "CrossingDetect." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/CrossingDetect.html.

APA

Wolfram Language. (2010). CrossingDetect. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/CrossingDetect.html

BibTeX

@misc{reference.wolfram_2024_crossingdetect, author="Wolfram Research", title="{CrossingDetect}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/CrossingDetect.html}", note=[Accessed: 22-November-2024 ]}

BibLaTeX

@online{reference.wolfram_2024_crossingdetect, organization={Wolfram Research}, title={CrossingDetect}, year={2014}, url={https://reference.wolfram.com/language/ref/CrossingDetect.html}, note=[Accessed: 22-November-2024 ]}