EdgeDetect

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`EdgeDetect`

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EdgeDetect[image]

finds edges in image and returns the result as a binary image.

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EdgeDetect[image,r]

finds edges at the scale of the specified pixel range r.

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EdgeDetect[image,r,t]

uses a threshold t for selecting image edges.

Details and Options

Edges of an image are a set of points between image regions and are typically computed by linking high-gradient pixels. In practice, an edge can have an arbitrary shape.
EdgeDetect uses gradient methods to find edges and works with arbitrary 2D and 3D images.
EdgeDetect[image] is equivalent to EdgeDetect[image,2].
The following range specifications r can be used:

	r	radius r in every dimension (default r=2)
	{r_row,r_col}	in 2D, range r_row in height, r_col in width
	{r_slice,r_row,r_col}	in 3D, range r_slice in height, r_row in depth, and r_col in width

EdgeDetect[image,r,t] uses hysteresis thresholding with a global threshold t. For additional forms of the threshold parameter, see the reference page for MorphologicalBinarize.
The following options can be specified:
Method Automatic edge detection method

Padding "Fixed" padding method
Possible settings for Method include:

	"Canny"	first-order directional Gaussian derivatives (default)
	"ShenCastan"	first-order derivatives of exponentials
	"Sobel"	binomial generalization of Sobel masks

By default, all straight and curved edges are returned. Selection of edges based on their straightness can be done by setting Method->{"method","StraightEdges"->s}. The default behavior is equivalent to "StraightEdges"->0. A setting "StraightEdges"->1 selects only the longest and strongest lines.
"StraightEdges" is ignored when used with Image3D objects.

Examples

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Basic Examples (1)Summary of the most common use cases

Detecting edges in a color image:

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https://wolfram.com/xid/0b0kzi65ody-zkbxj

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Scope (4)Survey of the scope of standard use cases

Find edges in a color image:

In[1]:=1

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https://wolfram.com/xid/0b0kzi65ody-8t432p

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Specify the scale of edges to detect:

In[1]:=1

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https://wolfram.com/xid/0b0kzi65ody-mzkcjn

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Specify larger scale to detect coarse features:

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https://wolfram.com/xid/0b0kzi65ody-i2omgu

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Edge selection using an explicit global threshold:

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https://wolfram.com/xid/0b0kzi65ody-nx1v0m

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Edges of a 3D image:

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https://wolfram.com/xid/0b0kzi65ody-4pr3v8

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https://wolfram.com/xid/0b0kzi65ody-9d455m

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Options (2)Common values & functionality for each option

Method (2)

Shen–Castan edge detection:

In[1]:=1

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https://wolfram.com/xid/0b0kzi65ody-xz6bqi

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By default, all edges are returned, regardless of their straightness:

In[1]:=1

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https://wolfram.com/xid/0b0kzi65ody-jdilx8

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Filter detected edges with their straightness:

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https://wolfram.com/xid/0b0kzi65ody-gxza5v

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Properties & Relations (1)Properties of the function, and connections to other functions

EdgeDetect might return edges that are thicker than one pixel:

In[1]:=1

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https://wolfram.com/xid/0b0kzi65ody-6egyrr

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Use Thinning to get single-pixel-wide edges:

In[2]:=2

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https://wolfram.com/xid/0b0kzi65ody-ypvsif

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