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

Field Summary

protected static int	INTEGER_MATH_SHIFT
protected static int	PATTERN_MATCH_RESULT_SCALE_FACTOR

Constructor Summary

OneDReader()

Method Summary

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 int	patternMatchVariance(int[] counters, int[] pattern, int 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

Field Detail

INTEGER_MATH_SHIFT

protected static final int INTEGER_MATH_SHIFT

See Also:

Constant Field Values

PATTERN_MATCH_RESULT_SCALE_FACTOR

protected static final int PATTERN_MATCH_RESULT_SCALE_FACTOR

See Also:

Constant Field Values

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 the barcode cannot be located or decoded for any reason

FormatException

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 the barcode cannot be located or decoded for any reason

FormatException

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 int patternMatchVariance(int[] counters,
                                          int[] pattern,
                                          int 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, where the ratio has been multiplied by 256. So, 0 means no variance (perfect match); 256 means the total variance between counters and patterns equals the pattern length, higher values mean even more variance

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 an error occurs or barcode cannot be found

ChecksumException

FormatException