CannyEdgeDetector (photonic3d API)

java.lang.Object
- org.area515.resinprinter.inkdetection.visual.CannyEdgeDetector

Direct Known Subclasses:

CannyEdgeDetector8BitGray
```
public class CannyEdgeDetector
extends java.lang.Object
```
This software has been released into the public domain. Please read the notes in this source file for additional information.

This class provides a configurable implementation of the Canny edge detection algorithm. This classic algorithm has a number of shortcomings, but remains an effective tool in many scenarios. This class is designed for single threaded use only.

Sample usage:
```
 //create the detector
 CannyEdgeDetector detector = new CannyEdgeDetector();
 //adjust its parameters as desired
 detector.setLowThreshold(0.5f);
 detector.setHighThreshold(1f);
 //apply it to an image
 detector.setSourceImage(frame);
 detector.process();
 BufferedImage edges = detector.getEdgesImage();
 
```
For a more complete understanding of this edge detector's parameters consult an explanation of the algorithm.

Field Summary

Fields
Modifier and Type Field and Description

protected java.awt.image.BufferedImage edgesImage

protected int height

protected int width

Fields
Modifier and Type	Field and Description
`protected java.awt.image.BufferedImage`	`edgesImage`
`protected int`	`height`
`protected int`	`width`

Constructor Summary

Constructors
Constructor and Description

CannyEdgeDetector()
Constructs a new detector with default parameters.

Constructors
Constructor and Description
`CannyEdgeDetector()` Constructs a new detector with default parameters.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`java.awt.image.BufferedImage`	`getEdgesImage()` Obtains an image containing the edges detected during the last call to the process method.
`float`	`getGaussianKernelRadius()` The radius of the Gaussian convolution kernel used to smooth the source image prior to gradient calculation.
`int`	`getGaussianKernelWidth()` The number of pixels across which the Gaussian kernel is applied.
`float`	`getHighThreshold()` The high threshold for hysteresis.
`float`	`getLowThreshold()` The low threshold for hysteresis.
`java.awt.image.BufferedImage`	`getSourceImage()` The image that provides the luminance data used by this detector to generate edges.
`boolean`	`isContrastNormalized()` Whether the luminance data extracted from the source image is normalized by linearizing its histogram prior to edge extraction.
`void`	`process()`
`void`	`setContrastNormalized(boolean contrastNormalized)` Sets whether the contrast is normalized
`void`	`setEdgesImage(java.awt.image.BufferedImage edgesImage)` Sets the edges image.
`void`	`setGaussianKernelRadius(float gaussianKernelRadius)` Sets the radius of the Gaussian convolution kernel used to smooth the source image prior to gradient calculation.
`void`	`setGaussianKernelWidth(int gaussianKernelWidth)` The number of pixels across which the Gaussian kernel is applied.
`void`	`setHighThreshold(float threshold)` Sets the high threshold for hysteresis.
`void`	`setLowThreshold(float threshold)` Sets the low threshold for hysteresis.
`void`	`setSourceImage(java.awt.image.BufferedImage image)` Specifies the image that will provide the luminance data in which edges will be detected.
`void`	`writeEdges(int[] pixels)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - height
```
protected int height
```
  - width
```
protected int width
```
  - edgesImage
```
protected java.awt.image.BufferedImage edgesImage
```
- Constructor Detail
  - CannyEdgeDetector
```
public CannyEdgeDetector()
```
    Constructs a new detector with default parameters.
- Method Detail
  - getSourceImage
```
public java.awt.image.BufferedImage getSourceImage()
```
    The image that provides the luminance data used by this detector to generate edges.
    
    Returns:
    
    the source image, or null
  - setSourceImage
```
public void setSourceImage(java.awt.image.BufferedImage image)
```
    Specifies the image that will provide the luminance data in which edges will be detected. A source image must be set before the process method is called.
    
    Parameters:
    
    image - a source of luminance data
  - getEdgesImage
```
public java.awt.image.BufferedImage getEdgesImage()
```
    Obtains an image containing the edges detected during the last call to the process method. The buffered image is an opaque image of type BufferedImage.TYPE_INT_ARGB in which edge pixels are white and all other pixels are black.
    
    Returns:
    
    an image containing the detected edges, or null if the process method has not yet been called.
  - setEdgesImage
```
public void setEdgesImage(java.awt.image.BufferedImage edgesImage)
```
    Sets the edges image. Calling this method will not change the operation of the edge detector in any way. It is intended to provide a means by which the memory referenced by the detector object may be reduced.
    
    Parameters:
    
    edgesImage - expected (though not required) to be null
  - getLowThreshold
```
public float getLowThreshold()
```
    The low threshold for hysteresis. The default value is 2.5.
    
    Returns:
    
    the low hysteresis threshold
  - setLowThreshold
```
public void setLowThreshold(float threshold)
```
    Sets the low threshold for hysteresis. Suitable values for this parameter must be determined experimentally for each application. It is nonsensical (though not prohibited) for this value to exceed the high threshold value.
    
    Parameters:
    
    threshold - a low hysteresis threshold
  - getHighThreshold
```
public float getHighThreshold()
```
    The high threshold for hysteresis. The default value is 7.5.
    
    Returns:
    
    the high hysteresis threshold
  - setHighThreshold
```
public void setHighThreshold(float threshold)
```
    Sets the high threshold for hysteresis. Suitable values for this parameter must be determined experimentally for each application. It is nonsensical (though not prohibited) for this value to be less than the low threshold value.
    
    Parameters:
    
    threshold - a high hysteresis threshold
  - getGaussianKernelWidth
```
public int getGaussianKernelWidth()
```
    The number of pixels across which the Gaussian kernel is applied. The default value is 16.
    
    Returns:
    
    the radius of the convolution operation in pixels
  - setGaussianKernelWidth
```
public void setGaussianKernelWidth(int gaussianKernelWidth)
```
    The number of pixels across which the Gaussian kernel is applied. This implementation will reduce the radius if the contribution of pixel values is deemed negligable, so this is actually a maximum radius.
    
    Parameters:
    
    gaussianKernelWidth - a radius for the convolution operation in pixels, at least 2.
  - getGaussianKernelRadius
```
public float getGaussianKernelRadius()
```
    The radius of the Gaussian convolution kernel used to smooth the source image prior to gradient calculation. The default value is 16.
    
    Returns:
    
    the Gaussian kernel radius in pixels
  - setGaussianKernelRadius
```
public void setGaussianKernelRadius(float gaussianKernelRadius)
```
    Sets the radius of the Gaussian convolution kernel used to smooth the source image prior to gradient calculation.
  - isContrastNormalized
```
public boolean isContrastNormalized()
```
    Whether the luminance data extracted from the source image is normalized by linearizing its histogram prior to edge extraction. The default value is false.
    
    Returns:
    
    whether the contrast is normalized
  - setContrastNormalized
```
public void setContrastNormalized(boolean contrastNormalized)
```
    Sets whether the contrast is normalized
    
    Parameters:
    
    contrastNormalized - true if the contrast should be normalized, false otherwise
  - process
```
public void process()
```
  - writeEdges
```
public void writeEdges(int[] pixels)
```

Class CannyEdgeDetector

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

height

width

edgesImage

Constructor Detail

CannyEdgeDetector

Method Detail

getSourceImage

setSourceImage

getEdgesImage

setEdgesImage

getLowThreshold

setLowThreshold

getHighThreshold

setHighThreshold

getGaussianKernelWidth

setGaussianKernelWidth

getGaussianKernelRadius

setGaussianKernelRadius

isContrastNormalized

setContrastNormalized

process

writeEdges