canny_Filter Class Reference
[Image Processing Filters, Single Frame, Edge Detection]

#include <canny_Filter.h>

Inheritance diagram for canny_Filter:

List of all members.

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Detailed Description

Canny Edge Detection.

This filter uses the canny method to detect the edges of an image.

The process includes the following steps:

1. 5x5 Gaussian mask for noise removal
2. Use Sobel masks to approximate gradient
3. Find orientation of gradient
4. Implement non-maximum suppression to assign edges
5. Hysteresis thresholding (2 thresholds: low and high)

An edge from this filter is a 0 value and a non-edge is 255.

The Gaussian mask can be turned on or off using canny_Filter::enableGaussian() or canny_Filter::disableGaussian().

The Sobel approximation can also be turned off, but this turns of the canny computation as well. Toggling the Sobel/Canny code is done with canny_Filter::enableSobelApprox() and canny_Filter::disableSobelApprox().

Supports the following formats:

• phImageRGB24
• phImageRGBA32
• phImageGREY8

The canny_Filter is a custom filter for Phission that outputs thicker lines than the OpenCV canny filter does.

Gaussian Ref: http://www.cee.hw.ac.uk/hipr/html/gsmooth.html

Sobel Ref: www.cee.hw.ac.uk/hipr/html/sobel.html

Todo:

add timing back into the filter

Make timing part of the phFilter class ???

verify all the algorithms in the canny_Filter

Output thin lines? or ar ethe thick ones good ?

When > 8bit channels are supported, make sure that the edge/non-edge values are appropriate minimum/maximum values

add example application code that shows how the processed images were output

Todo:

add example image inputs and processed image outputs

Definition at line 93 of file canny_Filter.h.

Public Member Functions
	canny_Filter (uint32_t lowThreshold=40, uint32_t highThreshold=120)
	~canny_Filter ()
int	set (uint32_t lowThreshold=40, uint32_t highThreshold=120)
void	enableGaussian (int enable=1)
void	disableGaussian (int disable=1)
void	enableSobelApprox (int enable=1)
void	disableSobelApprox (int disable=1)
phFilter *	cloneFilter ()
Protected Member Functions
int	filter ()
Private Attributes
uint32_t	m_lowThreshold
uint32_t	m_highThreshold
uint8_t *	m_gauss
uint8_t *	m_edge
uint32_t	m_gaussSize
uint32_t	m_edgeSize
int	m_useGaussian
int	m_useSobelApprox

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The documentation for this class was generated from the following files:

• filter/video/include/canny_Filter.h
• filter/video/src/canny_Filter.cpp

Copyright (C) 2002 - 2007

Philip D.S. Thoren ( pthoren@users.sourceforge.net ) University Of Massachusetts at Lowell Robotics Lab

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