com.jtm.qrcode.qrcode.detector

Class FinderPatternFinder

java.lang.Object

com.jtm.qrcode.qrcode.detector.FinderPatternFinder

public class FinderPatternFinder
extends java.lang.Object

This class attempts to find finder patterns in a QR Code. Finder patterns are the square markers at three corners of a QR Code. This class is thread-safe but not reentrant. Each thread must allocate its own object.

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	MAX_MODULES
protected static int	MIN_SKIP

Constructor Summary

Constructors

Constructor and Description
FinderPatternFinder(BitMatrix image) Creates a finder that will search the image for three finder patterns.
FinderPatternFinder(BitMatrix image, ResultPointCallback resultPointCallback)

Method Summary

Modifier and Type	Method and Description
protected static boolean	foundPatternCross(int[] stateCount)
protected BitMatrix	getImage()
protected java.util.List<FinderPattern>	getPossibleCenters()
protected boolean	handlePossibleCenter(int[] stateCount, int i, int j) This is called when a horizontal scan finds a possible alignment pattern.

Methods inherited from class java.lang.Object

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

Field Detail

MIN_SKIP

protected static final int MIN_SKIP

See Also:

Constant Field Values

MAX_MODULES

protected static final int MAX_MODULES

See Also:

Constant Field Values

Constructor Detail

FinderPatternFinder

public FinderPatternFinder(BitMatrix image)

Creates a finder that will search the image for three finder patterns.

Parameters:

image - image to search

FinderPatternFinder

public FinderPatternFinder(BitMatrix image,
                           ResultPointCallback resultPointCallback)

Method Detail

getImage

protected BitMatrix getImage()

getPossibleCenters

protected java.util.List<FinderPattern> getPossibleCenters()

foundPatternCross

protected static boolean foundPatternCross(int[] stateCount)

Parameters:

stateCount - count of black/white/black/white/black pixels just read

Returns:

true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios used by finder patterns to be considered a match

handlePossibleCenter

protected boolean handlePossibleCenter(int[] stateCount,
                                       int i,
                                       int j)

This is called when a horizontal scan finds a possible alignment pattern. It will cross check with a vertical scan, and if successful, will, ah, cross-cross-check with another horizontal scan. This is needed primarily to locate the real horizontal center of the pattern in cases of extreme skew. If that succeeds the finder pattern location is added to a list that tracks the number of times each location has been nearly-matched as a finder pattern. Each additional find is more evidence that the location is in fact a finder pattern center

Parameters:

stateCount - reading state module counts from horizontal scan

i - row where finder pattern may be found

j - end of possible finder pattern in row

Returns:

true if a finder pattern candidate was found this time