dlife.vision.filter
Class ConvolutionFilter

java.lang.Object
  java.util.Observable
      dlife.vision.filter.Filter
          dlife.vision.filter.ConvolutionFilter

Direct Known Subclasses:

GaussianFilter, LaplacianFilter

public class ConvolutionFilter
extends Filter

Filters an image by convolving a kernel over the image. A new value for each pixel is computed by placing the convolution kernel over the image with the pixel at the center. The values in the convolution kernel are then used to compute a weighted sum of the pixels covered by the kernel. The value of the pixel at the center of the kernel is then set to the weighted sum.

The ConvolutionFilter GUI (shown below) allows the user to enter values for a convolution kernel of up to 7x7. The 1x1 kernel below will make the image 1/2 as bright.

NOTES:

• The kernel is never placed off of the image. Thus, with a 3x3 kernel there will be a border 1 pixel wide which is not processed. All non-processed pixels are set to black.
• If the kernel is all zeros then the convolution is not performed. (Seems like it should generate a black image, but the Java ConvolveOp implementation crashes!)

The convolution operation forms the basis for a wide variety of image filters. For example the GaussianFilter and LaplacianFilter are both sub-classes of the ConvolutionFilter. More information and a brief introduction to Convolution Matrices (filters) can be found in the gimp manual (Note: the writing on this page is a little rough, but it provides a good feel for convolution filters).

Version:

Jul 10, 2008

Author:

Grant Braught, Dickinson College

Nested Class Summary

protected class

ConvolutionFilter.ConvolutionFilterGUI GUI for a ConvolutionFilter.

Constructor Summary

ConvolutionFilter()
Construct a new ConvolutionFilter.

ConvolutionFilter(float[][] kernel, int pixelRow, int pixelCol)
Construct a new ConvolutionFilter using the specified kernel.

Method Summary

protected FilterGUI	createGUIObject() Get the GUI for this ConvolutionFilter.
BufferedImage	filter(BufferedImage frame) Apply the convolution kernel to the image in frame and return the result.
String	getCode(String name) Get a String containing the Java code that would be necessary to create this Filter in its current state and add it to the specified VisionClient.
float[][]	getKernel() Get the convolution kernel from this ConvolutionFilter.
static void	main(String[] args) Main method that pops up a GUI for the ConvolutionFilter to allow it to be tested.
void	setKernel(float[][] newKernel, int pixelRow, int pixelCol) Set the convolution kernel for this ConvolutionFilter.
void	setKernelCell(int row, int col, float value) Set the value of one of the cells in the convolution kernel for this ConvolutionFilter.

Methods inherited from class dlife.vision.filter.Filter

getGUI, getID, isOn, turnOn

Methods inherited from class java.util.Observable

addObserver, clearChanged, countObservers, deleteObserver, deleteObservers, hasChanged, notifyObservers, notifyObservers, setChanged

Methods inherited from class java.lang.Object

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

Constructor Detail

ConvolutionFilter

public ConvolutionFilter()

Construct a new ConvolutionFilter.

ConvolutionFilter

public ConvolutionFilter(float[][] kernel,
                         int pixelRow,
                         int pixelCol)

Construct a new ConvolutionFilter using the specified kernel. The elements of kernel are copied into the kernel of this ConvolutionFilter. The element at pixelRow,pixelCol appears at the center of this ConvolutionFilter. Any elements of the provided kernel that do not fit within a 7x7 kernel are ignored. An elements of the 7x7 kernel that are not specified are set to 0.

Parameters:

kernel - the convolution kernel.

pixelRow - the index of the element of kernel that is over the pixel currently being processed.

pixelCol - the index of the element of kernel that is over the pixel currently being processed.

Method Detail

createGUIObject

protected FilterGUI createGUIObject()

Get the GUI for this ConvolutionFilter.

Specified by:

createGUIObject in class Filter

Returns:

a reference to the GUI.

getKernel

public float[][] getKernel()

Get the convolution kernel from this ConvolutionFilter.

Returns:

the kernel as a 7x7 array of double values.

setKernel

public void setKernel(float[][] newKernel,
                      int pixelRow,
                      int pixelCol)

Set the convolution kernel for this ConvolutionFilter.

Parameters:

newKernel - the new kernel.

pixelRow - the index of the element of kernel that is over the pixel currently being processed.

pixelCol - the index of the element of kernel that is over the pixel currently being processed.

setKernelCell

public void setKernelCell(int row,
                          int col,
                          float value)

Set the value of one of the cells in the convolution kernel for this ConvolutionFilter.

Parameters:

row - the row of the cell to set.

col - the column of the cell to set.

value - the value to place in the cell.

filter

public BufferedImage filter(BufferedImage frame)

Apply the convolution kernel to the image in frame and return the result. If the convolution kernel is all 0's then the original image is returned unfiltered.

Specified by:

filter in class Filter

Parameters:

frame - the image to be filtered.

Returns:

the filtered image.

getCode

public String getCode(String name)

Get a String containing the Java code that would be necessary to create this Filter in its current state and add it to the specified VisionClient. The code generated should use the ID of this filter as part of any variable name to ensure that its variables have a unique identifier.

Specified by:

getCode in class Filter

Parameters:

name - the name of the Camera device to which the generated code should add the Filter.

Returns:

the Java code to create this Filter.

main

public static void main(String[] args)
                 throws Exception

Main method that pops up a GUI for the ConvolutionFilter to allow it to be tested.

Parameters:

args - none

Throws:

Exception