Class Detector
- Direct Known Subclasses:
MultiDetector
Encapsulates logic that can detect a QR Code in an image, even if the QR Code is rotated or skewed, or partially obscured.
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Field Summary
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprotected 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.private float
calculateModuleSizeOneWay
(ResultPoint pattern, ResultPoint otherPattern) Estimates module size based on two finder patterns -- it usessizeOfBlackWhiteBlackRunBothWays(int, int, int, int)
to figure the width of each, measuring along the axis between their centers.private static int
computeDimension
(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft, float moduleSize) Computes the dimension (number of modules on a size) of the QR Code based on the position of the finder patterns and estimated module size.private static PerspectiveTransform
createTransform
(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft, ResultPoint alignmentPattern, int dimension) detect()
Detects a QR Code in an image.final DetectorResult
detect
(Map<DecodeHintType, ?> hints) Detects a QR Code in an image.protected final 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 final BitMatrix
getImage()
protected final ResultPointCallback
protected final DetectorResult
private static BitMatrix
sampleGrid
(BitMatrix image, PerspectiveTransform transform, int dimension) private float
sizeOfBlackWhiteBlackRun
(int fromX, int fromY, int toX, int toY) This method traces a line from a point in the image, in the direction towards another point.private float
sizeOfBlackWhiteBlackRunBothWays
(int fromX, int fromY, int toX, int toY) SeesizeOfBlackWhiteBlackRun(int, int, int, int)
; computes the total width of a finder pattern by looking for a black-white-black run from the center in the direction of another point (another finder pattern center), and in the opposite direction too.
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Field Details
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image
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resultPointCallback
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Constructor Details
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Detector
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Method Details
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getImage
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getResultPointCallback
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detect
Detects a QR Code in an image.
- Returns:
DetectorResult
encapsulating results of detecting a QR Code- Throws:
NotFoundException
- if QR Code cannot be foundFormatException
- if a QR Code cannot be decoded
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detect
public final DetectorResult detect(Map<DecodeHintType, ?> hints) throws NotFoundException, FormatExceptionDetects 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 foundFormatException
- if a QR Code cannot be decoded
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processFinderPatternInfo
protected final DetectorResult processFinderPatternInfo(FinderPatternInfo info) throws NotFoundException, FormatException - Throws:
NotFoundException
FormatException
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createTransform
private static PerspectiveTransform createTransform(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft, ResultPoint alignmentPattern, int dimension) -
sampleGrid
private static BitMatrix sampleGrid(BitMatrix image, PerspectiveTransform transform, int dimension) throws NotFoundException - Throws:
NotFoundException
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computeDimension
private static int computeDimension(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft, float moduleSize) throws NotFoundException Computes the dimension (number of modules on a size) of the QR Code based on the position of the finder patterns and estimated module size.
- Throws:
NotFoundException
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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 centertopRight
- detected top-right finder pattern centerbottomLeft
- detected bottom-left finder pattern center- Returns:
- estimated module size
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calculateModuleSizeOneWay
Estimates module size based on two finder patterns -- it uses
sizeOfBlackWhiteBlackRunBothWays(int, int, int, int)
to figure the width of each, measuring along the axis between their centers. -
sizeOfBlackWhiteBlackRunBothWays
private float sizeOfBlackWhiteBlackRunBothWays(int fromX, int fromY, int toX, int toY) SeesizeOfBlackWhiteBlackRun(int, int, int, int)
; computes the total width of a finder pattern by looking for a black-white-black run from the center in the direction of another point (another finder pattern center), and in the opposite direction too. -
sizeOfBlackWhiteBlackRun
private float sizeOfBlackWhiteBlackRun(int fromX, int fromY, int toX, int toY) This method traces a line from a point in the image, in the direction towards another point. It begins in a black region, and keeps going until it finds white, then black, then white again. It reports the distance from the start to this point.
This is used when figuring out how wide a finder pattern is, when the finder pattern may be skewed or rotated.
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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 farestAlignmentX
- x coordinate of center of area probably containing alignment patternestAlignmentY
- y coordinate of aboveallowanceFactor
- 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
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