Package edu.gsu.cs.dmlab.imageproc.edgedetection.util

Class NonMaximumSuppression

java.lang.Object

edu.gsu.cs.dmlab.imageproc.edgedetection.util.NonMaximumSuppression

public class NonMaximumSuppression
extends Object

OVERVIEW: Edges in images are usually to defined to be 1 pixel thick. Thus, we cannot simply look for pixels at which place the change in intensity is sufficiently large (greater than a threshold). We must also suppress non-maximum pixels. Essentially, we calculate the edge direction (direction in which gradient of pixel intensity is greatest). We round the edge direction to the nearest 45 degrees. (i, j) is suppressed if either of the pixels one unit in the edge direction have greater gradient magnitudes than (i, j).

Author:

Jason Altschuler, modified by Azim Ahmadzadeh of Data Mining Lab, Georgia State University

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	NonMaximumSuppression.EdgeDirection	Direction to check non-maximum suppression

Constructor Summary

Constructors

Constructor	Description
NonMaximumSuppression()

Method Summary

Modifier and Type	Method	Description
static int[]	indicesMaxSuppresion(NonMaximumSuppression.EdgeDirection d, int i, int j)	Get coordinates of the two points needed to check for non-maximum suppression.
static boolean	nonMaximumSuppression(double[][] mag, NonMaximumSuppression.EdgeDirection angle, int i, int j)	See if pixel at (i, j) is an edge.

Methods inherited from class java.lang.Object

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

Constructor Detail

NonMaximumSuppression

public NonMaximumSuppression()

Method Detail

nonMaximumSuppression

public static boolean nonMaximumSuppression(double[][] mag,
                                            NonMaximumSuppression.EdgeDirection angle,
                                            int i,
                                            int j)

See if pixel at (i, j) is an edge. Requires the following two criteria:

1. mag[i][j] > threshold

2. Non-maximum suppression

Parameters:

mag -

angle -

i -

j -

Returns:

indicesMaxSuppresion

public static int[] indicesMaxSuppresion(NonMaximumSuppression.EdgeDirection d,
                                         int i,
                                         int j)

Get coordinates of the two points needed to check for non-maximum suppression.

Parameters:

d -

i -

j -

Returns:

{i1, j1, i2, j2}