System object: visionhdl.EdgeDetector
Package: visionhdl
Detect edges at an image pixel
[edge,ctrlOut] = step(detect_edges,pixelIn,ctrlIn)
[G1,G2,ctrlOut] = step(detect_edges,pixelIn,ctrlIn)
[edge,ctrlOut] = step(detect_edges,pixelIn,ctrlIn,thresh)
Note
Starting in R2016b, instead of using the step method
to perform the operation defined by the System object™, you can
call the object with arguments, as if it were a function. For example, y
= step(obj,x) and y = obj(x) perform
equivalent operations.
[edge,ctrlOut] = step(detect_edges,pixelIn,ctrlIn) detects
edges in the neighborhood of pixelIn by computing
the gradient in two orthogonal directions. The edge output
argument is a binary value indicating whether the sum of the squares
of the gradients for the input pixel is above the threshold indicating
an edge.
[G1,G2,ctrlOut] = step(detect_edges,pixelIn,ctrlIn) detects
edges in the neighborhood of pixelIn by computing
the gradient in two orthogonal directions. Use this syntax when you
set GradientComponentOutputPorts property to true.
The G1 and G2 output arguments
are the gradients calculated in the two orthogonal directions. When
you set the Method property to 'Sobel' or 'Prewitt',
the first argument is the vertical gradient, and the second argument
is the horizontal gradient. When you set the Method property
to 'Roberts', the first argument is the 45 degree
gradient, and the second argument is the 135 degree gradient.
[edge,ctrlOut] = step(detect_edges,pixelIn,ctrlIn,thresh) detects
edges in the neighborhood of pixelIn by computing
the gradient in two orthogonal directions. Use this syntax when you
set ThresholdSource property to 'InputPort'.
The edge output argument is a binary value indicating
whether the sum of the squares of the gradients was above the threshold, thresh,
squared.
You can use any combination of the optional port syntaxes.
This object uses a streaming pixel interface with a structure
for frame control signals. This interface enables the object to operate independently of image
size and format, and to connect with other Vision HDL Toolbox™ objects. The object accepts and returns a scalar pixel value and control signals
as a structure containing five signals. The control signals indicate the validity of each pixel
and its location in the frame. To convert a pixel matrix into a pixel stream and control
signals, use the visionhdl.FrameToPixels object. For a full
description of the interface, see Streaming Pixel Interface.
Note
The System object performs an initialization the first time
you call the step method. This initialization locks
nontunable properties and input specifications, such as dimensions,
complexity, and data type of the input data. If you change a nontunable
property or an input specification, the object issues an error. To
change nontunable properties or inputs, first call the release method
to unlock the object.