com.google.zxing.qrcode.detector

Class Detector

java.lang.Object

com.google.zxing.qrcode.detector.Detector

Direct Known Subclasses:

MultiDetector

public class Detector
extends Object

Encapsulates logic that can detect a QR Code in an image, even if the QR Code is rotated or skewed, or partially obscured.

Author:

Sean Owen

Constructor Summary

Constructors

Constructor and Description
Detector(BitMatrix image)

Method Summary

Modifier and Type	Method and Description
protected float	calculateModuleSize(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft) Computes an average estimated module size based on estimated derived from the positions of the three finder patterns.
DetectorResult	detect() Detects a QR Code in an image.
DetectorResult	detect(Map<DecodeHintType,?> hints) Detects a QR Code in an image.
protected AlignmentPattern	findAlignmentInRegion(float overallEstModuleSize, int estAlignmentX, int estAlignmentY, float allowanceFactor) Attempts to locate an alignment pattern in a limited region of the image, which is guessed to contain it.
protected BitMatrix	getImage()
protected ResultPointCallback	getResultPointCallback()
protected DetectorResult	processFinderPatternInfo(FinderPatternInfo info)

Methods inherited from class java.lang.Object

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

Constructor Detail

Detector

public Detector(BitMatrix image)

Method Detail

getImage

protected final BitMatrix getImage()

getResultPointCallback

protected final ResultPointCallback getResultPointCallback()

detect

public DetectorResult detect()
                      throws NotFoundException,
                             FormatException

Detects a QR Code in an image.

Returns:

DetectorResult encapsulating results of detecting a QR Code

Throws:

NotFoundException - if QR Code cannot be found

FormatException - if a QR Code cannot be decoded

detect

public final DetectorResult detect(Map<DecodeHintType,?> hints)
                            throws NotFoundException,
                                   FormatException

Detects a QR Code in an image.

Parameters:

hints - optional hints to detector

Returns:

DetectorResult encapsulating results of detecting a QR Code

Throws:

NotFoundException - if QR Code cannot be found

FormatException - if a QR Code cannot be decoded

processFinderPatternInfo

protected final DetectorResult processFinderPatternInfo(FinderPatternInfo info)
                                                 throws NotFoundException,
                                                        FormatException

Throws:

NotFoundException

FormatException

calculateModuleSize

protected final float calculateModuleSize(ResultPoint topLeft,
                                          ResultPoint topRight,
                                          ResultPoint bottomLeft)

Computes an average estimated module size based on estimated derived from the positions of the three finder patterns.

Parameters:

topLeft - detected top-left finder pattern center

topRight - detected top-right finder pattern center

bottomLeft - detected bottom-left finder pattern center

Returns:

estimated module size

findAlignmentInRegion

protected final AlignmentPattern findAlignmentInRegion(float overallEstModuleSize,
                                                       int estAlignmentX,
                                                       int estAlignmentY,
                                                       float allowanceFactor)
                                                throws NotFoundException

Attempts to locate an alignment pattern in a limited region of the image, which is guessed to contain it. This method uses AlignmentPattern.

Parameters:

overallEstModuleSize - estimated module size so far

estAlignmentX - x coordinate of center of area probably containing alignment pattern

estAlignmentY - y coordinate of above

allowanceFactor - number of pixels in all directions to search from the center

Returns:

AlignmentPattern if found, or null otherwise

Throws:

NotFoundException - if an unexpected error occurs during detection