org.openimaj.image.processing.edges

Class CannyEdgeDetector

java.lang.Object

org.openimaj.image.processing.edges.CannyEdgeDetector

All Implemented Interfaces:

ImageProcessor<FImage>, Processor<FImage>, SinglebandImageProcessor<Float,FImage>

public class CannyEdgeDetector
extends Object
implements SinglebandImageProcessor<Float,FImage>

Canny edge detector. Performs the following steps:

1. Gaussian blur with std.dev. sigma
2. Horizontal and vertical edge detection with Sobel operators
3. Non-maximum suppression
4. Hysteresis thresholding

The upper and lower thresholds for the hysteresis thresholding can be specified manually or automatically chosen based on the histogram of the edge magnitudes.

Author:

Jonathon Hare (jsh2@ecs.soton.ac.uk), Sina Samangooei (ss@ecs.soton.ac.uk)

Nested Class Summary

Nested classes/interfaces inherited from interface org.openimaj.image.processor.SinglebandImageProcessor

SinglebandImageProcessor.Processable<T,S extends Image<T,S>,I extends Image<?,I>>

Constructor Summary

Constructors

Constructor and Description
CannyEdgeDetector() Default constructor.
CannyEdgeDetector(float sigma) Construct with the give sigma.
CannyEdgeDetector(float lowThresh, float highThresh, float sigma) Construct with all parameters set manually.

Method Summary

Modifier and Type	Method and Description
void	processImage(FImage image) Process an image.
void	processImage(FImage output, FImage dx, FImage dy) Apply non-max suppression and hysteresis thresholding based on the given (Sobel) gradient maps and write the result to the given output image.
void	processImage(FImage image, FSobel sobel) Apply non-max suppression and hysteresis thresholding based using the given FSobel analyser to generate the gradients.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CannyEdgeDetector

public CannyEdgeDetector()

Default constructor. Sigma is set to 1.0, and the thresholds are chosen automatically.

CannyEdgeDetector

public CannyEdgeDetector(float sigma)

Construct with the give sigma. The thresholds are chosen automatically.

Parameters:

sigma - the amount of initial blurring

CannyEdgeDetector

public CannyEdgeDetector(float lowThresh,
                         float highThresh,
                         float sigma)

Construct with all parameters set manually.

Parameters:

lowThresh - lower hysteresis threshold.

highThresh - upper hysteresis threshold.

sigma - the amount of initial blurring.

Method Detail

processImage

public void processImage(FImage image)

Description copied from interface: ImageProcessor

Process an image. Implementing classes must alter the image passed in-place or assign the output to the input using Image.internalAssign(Image).

Specified by:

processImage in interface ImageProcessor<FImage>

Parameters:

image - The image to process in place.

processImage

public void processImage(FImage image,
                         FSobel sobel)

Apply non-max suppression and hysteresis thresholding based using the given FSobel analyser to generate the gradients. The gradient maps held by the FSobel object will be set to the gradients of the input image after this method returns.

Parameters:

image - the image to process (and write the result to)

sobel - the computed gradients

processImage

public void processImage(FImage output,
                         FImage dx,
                         FImage dy)

Apply non-max suppression and hysteresis thresholding based on the given (Sobel) gradient maps and write the result to the given output image.

Parameters:

output - the output image

dx - the x gradients

dy - the y gradients