Package com.google.zxing.aztec.detector

Class Detector

java.lang.Object

com.google.zxing.aztec.detector.Detector

public final class Detector
extends java.lang.Object

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

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	Detector.CorrectedParameter
(package private) static class	Detector.Point

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	compact
private static int[]	EXPECTED_CORNER_BITS
private BitMatrix	image
private int	nbCenterLayers
private int	nbDataBlocks
private int	nbLayers
private int	shift

Constructor Summary

Constructors

Constructor	Description
Detector(BitMatrix image)

Method Summary

Modifier and Type	Method	Description
AztecDetectorResult	detect()
AztecDetectorResult	detect(boolean isMirror)	Detects an Aztec Code in an image.
private static float	distance(Detector.Point a, Detector.Point b)
private static float	distance(ResultPoint a, ResultPoint b)
private static ResultPoint[]	expandSquare(ResultPoint[] cornerPoints, int oldSide, int newSide)	Expand the square represented by the corner points by pushing out equally in all directions
private int	extractParameters(ResultPoint[] bullsEyeCorners)	Extracts the number of data layers and data blocks from the layer around the bull's eye.
private ResultPoint[]	getBullsEyeCorners(Detector.Point pCenter)	Finds the corners of a bull-eye centered on the passed point.
private int	getColor(Detector.Point p1, Detector.Point p2)	Gets the color of a segment
private static Detector.CorrectedParameter	getCorrectedParameterData(long parameterData, boolean compact)	Corrects the parameter bits using Reed-Solomon algorithm.
private int	getDimension()
private Detector.Point	getFirstDifferent(Detector.Point init, boolean color, int dx, int dy)	Gets the coordinate of the first point with a different color in the given direction
private Detector.Point	getMatrixCenter()	Finds a candidate center point of an Aztec code from an image
private ResultPoint[]	getMatrixCornerPoints(ResultPoint[] bullsEyeCorners)	Gets the Aztec code corners from the bull's eye corners and the parameters.
private static int	getRotation(int[] sides, int length)
private boolean	isValid(int x, int y)
private boolean	isValid(ResultPoint point)
private boolean	isWhiteOrBlackRectangle(Detector.Point p1, Detector.Point p2, Detector.Point p3, Detector.Point p4)
private BitMatrix	sampleGrid(BitMatrix image, ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomRight, ResultPoint bottomLeft)	Creates a BitMatrix by sampling the provided image.
private int	sampleLine(ResultPoint p1, ResultPoint p2, int size)	Samples a line.

Methods inherited from class java.lang.Object

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

Field Detail

EXPECTED_CORNER_BITS

private static final int[] EXPECTED_CORNER_BITS

image

private final BitMatrix image

compact

private boolean compact

nbLayers

private int nbLayers

nbDataBlocks

private int nbDataBlocks

nbCenterLayers

private int nbCenterLayers

shift

private int shift

Constructor Detail

Detector

public Detector(BitMatrix image)

Method Detail

detect

public AztecDetectorResult detect()
                           throws NotFoundException

Throws:

NotFoundException

detect

public AztecDetectorResult detect(boolean isMirror)
                           throws NotFoundException

Detects an Aztec Code in an image.

Parameters:

isMirror - if true, image is a mirror-image of original

Returns:

AztecDetectorResult encapsulating results of detecting an Aztec Code

Throws:

NotFoundException - if no Aztec Code can be found

extractParameters

private int extractParameters(ResultPoint[] bullsEyeCorners)
                       throws NotFoundException

Extracts the number of data layers and data blocks from the layer around the bull's eye.

Parameters:

bullsEyeCorners - the array of bull's eye corners

Returns:

the number of errors corrected during parameter extraction

Throws:

NotFoundException - in case of too many errors or invalid parameters

getRotation

private static int getRotation(int[] sides,
                               int length)
                        throws NotFoundException

Throws:

NotFoundException

getCorrectedParameterData

private static Detector.CorrectedParameter getCorrectedParameterData(long parameterData,
                                                                     boolean compact)
                                                              throws NotFoundException

Corrects the parameter bits using Reed-Solomon algorithm.

Parameters:

parameterData - parameter bits

compact - true if this is a compact Aztec code

Returns:

the corrected parameter

Throws:

NotFoundException - if the array contains too many errors

getBullsEyeCorners

private ResultPoint[] getBullsEyeCorners(Detector.Point pCenter)
                                  throws NotFoundException

Finds the corners of a bull-eye centered on the passed point. This returns the centers of the diagonal points just outside the bull's eye Returns [topRight, bottomRight, bottomLeft, topLeft]

Parameters:

pCenter - Center point

Returns:

The corners of the bull-eye

Throws:

NotFoundException - If no valid bull-eye can be found

getMatrixCenter

private Detector.Point getMatrixCenter()

Finds a candidate center point of an Aztec code from an image

Returns:

the center point

getMatrixCornerPoints

private ResultPoint[] getMatrixCornerPoints(ResultPoint[] bullsEyeCorners)

Gets the Aztec code corners from the bull's eye corners and the parameters.

Parameters:

bullsEyeCorners - the array of bull's eye corners

Returns:

the array of aztec code corners

sampleGrid

private BitMatrix sampleGrid(BitMatrix image,
                             ResultPoint topLeft,
                             ResultPoint topRight,
                             ResultPoint bottomRight,
                             ResultPoint bottomLeft)
                      throws NotFoundException

Creates a BitMatrix by sampling the provided image. topLeft, topRight, bottomRight, and bottomLeft are the centers of the squares on the diagonal just outside the bull's eye.

Throws:

NotFoundException

sampleLine

private int sampleLine(ResultPoint p1,
                       ResultPoint p2,
                       int size)

Samples a line.

Parameters:

p1 - start point (inclusive)

p2 - end point (exclusive)

size - number of bits

Returns:

the array of bits as an int (first bit is high-order bit of result)

isWhiteOrBlackRectangle

private boolean isWhiteOrBlackRectangle(Detector.Point p1,
                                        Detector.Point p2,
                                        Detector.Point p3,
                                        Detector.Point p4)

Returns:

true if the border of the rectangle passed in parameter is compound of white points only or black points only

getColor

private int getColor(Detector.Point p1,
                     Detector.Point p2)

Gets the color of a segment

Returns:

1 if segment more than 90% black, -1 if segment is more than 90% white, 0 else

getFirstDifferent

private Detector.Point getFirstDifferent(Detector.Point init,
                                         boolean color,
                                         int dx,
                                         int dy)

Gets the coordinate of the first point with a different color in the given direction

expandSquare

private static ResultPoint[] expandSquare(ResultPoint[] cornerPoints,
                                          int oldSide,
                                          int newSide)

Expand the square represented by the corner points by pushing out equally in all directions

Parameters:

cornerPoints - the corners of the square, which has the bull's eye at its center

oldSide - the original length of the side of the square in the target bit matrix

newSide - the new length of the size of the square in the target bit matrix

Returns:

the corners of the expanded square

isValid

private boolean isValid(int x,
                        int y)

isValid

private boolean isValid(ResultPoint point)

distance

private static float distance(Detector.Point a,
                              Detector.Point b)

distance

private static float distance(ResultPoint a,
                              ResultPoint b)

getDimension

private int getDimension()