Edge

Last modified: November 20, 2009

Contents

canny_edge_image

Image [GreyScale|Grey16|Float] canny_edge_image (float(0.00, 1e+300) scale = 0.80, float(0.00, 1e+300) gradient_threshold = 4.00)

Operates on:Image [GreyScale|Grey16|Float]
Returns:Image [GreyScale|Grey16|Float]
Category:Edge
Defined in:edgedetect.py
Author:Ullrich Köthe (wrapped by Robert Ferguson)

EXPERIMENTAL

Detect and mark edges in an edge image using Canny's algorithm.

Uses code from the VIGRA Computer Vision Library (Copyright 1998-2007 by Ullrich Köthe).

scale
The scale relates to the value b of the exponential filter.
gradient_threshold
This operator first calls cannyEdgelList() to generate an edgel list for the given image. Than it scans this list and selects edgels whose strength is above the given gradient_threshold.

Example 1: canny_edge_image()

images/GreyScale_generic.png images/canny_edge_image_plugin_00.png

difference_of_exponential_crack_edge_image

Image [GreyScale|Grey16|Float] difference_of_exponential_crack_edge_image (float(0.00, 1e+300) scale = 0.80, float(0.00, 1e+300) gradient_threshold = 4.00, int(0, 32000) min_edge_length = 0, bool close_gaps = False, bool beautify = False)

Operates on:Image [GreyScale|Grey16|Float]
Returns:Image [GreyScale|Grey16|Float]
Category:Edge
Defined in:edgedetect.py
Author:Ullrich Köthe (wrapped by Robert Ferguson)

EXPERIMENTAL

Detect and mark edges in a crack edge image using the Shen/Castan zero-crossing detector.

Uses code from the VIGRA Computer Vision Library (Copyright 1998-2007 by Ullrich Köthe).

scale
The scale relates to the value b of the exponential filter.
gradient_threshold
Whenever the gradient at a zero crossing is greater than the given gradient threshold, an edge point is marked in the destination image on the darker side of the zero crossing (the zero crossing occurs between pixels).
min_edge_length
Removes all edges shorter than the number of pixels specified (0 retains all edges). Values near 10 are suggested.
close_gaps
Close one pixel wide gaps.
beautify
See the VIGRA Docs.

Example 1: difference_of_exponential_crack_edge_image()

images/GreyScale_generic.png images/difference_of_exponential_crack_edge_image_plugin_00.png

difference_of_exponential_edge_image

Image [GreyScale|Grey16|Float] difference_of_exponential_edge_image (float(0.00, 1e+300) scale = 0.80, float(0.00, 1e+300) gradient_threshold = 4.00, int(0, 32000) min_edge_length = 0)

Operates on:Image [GreyScale|Grey16|Float]
Returns:Image [GreyScale|Grey16|Float]
Category:Edge
Defined in:edgedetect.py
Author:Ullrich Köthe (wrapped by Robert Ferguson)

EXPERIMENTAL

Detect and mark edges in an edge image using the Shen/Castan zero-crossing detector.

Uses code from the VIGRA Computer Vision Library (Copyright 1998-2007 by Ullrich Köthe).

scale
The scale relates to the value b of the exponential filter.
gradient_threshold
Whenever the gradient at a zero crossing is greater than the given gradient_threshold, an edge point is marked in the destination image on the darker side of the zero crossing (the zero crossing occurs between pixels).
min_edge_length
Removes all edges shorter than the number of pixels specified (0 retains all edges). Values near 10 are suggested.

Example 1: difference_of_exponential_edge_image()

images/GreyScale_generic.png images/difference_of_exponential_edge_image_plugin_00.png