com.google.zxing.oned

Class OneDReader

java.lang.Object

com.google.zxing.oned.OneDReader

All Implemented Interfaces:

Reader

Direct Known Subclasses:

AbstractRSSReader, CodaBarReader, Code128Reader, Code39Reader, Code93Reader, ITFReader, MultiFormatOneDReader, MultiFormatUPCEANReader, UPCEANReader

public abstract class OneDReader
extends Object
implements Reader

Encapsulates functionality and implementation that is common to all families of one-dimensional barcodes.

Author:

dswitkin@google.com (Daniel Switkin), Sean Owen

Constructor Summary

Constructors

Constructor and Description
OneDReader()

Method Summary

Modifier and Type	Method and Description
Result	decode(BinaryBitmap image) Locates and decodes a barcode in some format within an image.
Result	decode(BinaryBitmap image, Map<DecodeHintType,?> hints) Locates and decodes a barcode in some format within an image.
abstract Result	decodeRow(int rowNumber, BitArray row, Map<DecodeHintType,?> hints) Attempts to decode a one-dimensional barcode format given a single row of an image.
protected static float	patternMatchVariance(int[] counters, int[] pattern, float maxIndividualVariance) Determines how closely a set of observed counts of runs of black/white values matches a given target pattern.
protected static void	recordPattern(BitArray row, int start, int[] counters) Records the size of successive runs of white and black pixels in a row, starting at a given point.
protected static void	recordPatternInReverse(BitArray row, int start, int[] counters)
void	reset() Resets any internal state the implementation has after a decode, to prepare it for reuse.

Methods inherited from class java.lang.Object

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

Constructor Detail

OneDReader

public OneDReader()

Method Detail

decode

public Result decode(BinaryBitmap image)
              throws NotFoundException,
                     FormatException

Description copied from interface: Reader

Locates and decodes a barcode in some format within an image.

Specified by:

decode in interface Reader

Parameters:

image - image of barcode to decode

Returns:

String which the barcode encodes

Throws:

NotFoundException - if no potential barcode is found

FormatException - if a potential barcode is found but format is invalid

decode

public Result decode(BinaryBitmap image,
                     Map<DecodeHintType,?> hints)
              throws NotFoundException,
                     FormatException

Description copied from interface: Reader

Locates and decodes a barcode in some format within an image. This method also accepts hints, each possibly associated to some data, which may help the implementation decode.

Specified by:

decode in interface Reader

Parameters:

image - image of barcode to decode

hints - passed as a Map from DecodeHintType to arbitrary data. The meaning of the data depends upon the hint type. The implementation may or may not do anything with these hints.

Returns:

String which the barcode encodes

Throws:

NotFoundException - if no potential barcode is found

FormatException - if a potential barcode is found but format is invalid

reset

public void reset()

Description copied from interface: Reader

Resets any internal state the implementation has after a decode, to prepare it for reuse.

Specified by:

reset in interface Reader

recordPattern

protected static void recordPattern(BitArray row,
                                    int start,
                                    int[] counters)
                             throws NotFoundException

Records the size of successive runs of white and black pixels in a row, starting at a given point. The values are recorded in the given array, and the number of runs recorded is equal to the size of the array. If the row starts on a white pixel at the given start point, then the first count recorded is the run of white pixels starting from that point; likewise it is the count of a run of black pixels if the row begin on a black pixels at that point.

Parameters:

row - row to count from

start - offset into row to start at

counters - array into which to record counts

Throws:

NotFoundException - if counters cannot be filled entirely from row before running out of pixels

recordPatternInReverse

protected static void recordPatternInReverse(BitArray row,
                                             int start,
                                             int[] counters)
                                      throws NotFoundException

Throws:

NotFoundException

patternMatchVariance

protected static float patternMatchVariance(int[] counters,
                                            int[] pattern,
                                            float maxIndividualVariance)

Determines how closely a set of observed counts of runs of black/white values matches a given target pattern. This is reported as the ratio of the total variance from the expected pattern proportions across all pattern elements, to the length of the pattern.

Parameters:

counters - observed counters

pattern - expected pattern

maxIndividualVariance - The most any counter can differ before we give up

Returns:

ratio of total variance between counters and pattern compared to total pattern size

decodeRow

public abstract Result decodeRow(int rowNumber,
                                 BitArray row,
                                 Map<DecodeHintType,?> hints)
                          throws NotFoundException,
                                 ChecksumException,
                                 FormatException

Attempts to decode a one-dimensional barcode format given a single row of an image.

Parameters:

rowNumber - row number from top of the row

row - the black/white pixel data of the row

hints - decode hints

Returns:

Result containing encoded string and start/end of barcode

Throws:

NotFoundException - if no potential barcode is found

ChecksumException - if a potential barcode is found but does not pass its checksum

FormatException - if a potential barcode is found but format is invalid