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 .
• Using the option setting , 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 :

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: 24-May-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: 24-May-2024 ]}