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.

  • Constructor Details

    • OneDReader

      public OneDReader()

  • Method Details

    • 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

    • doDecode

      private Result doDecode(BinaryBitmap image, Map<DecodeHintType, ?> hints) throws NotFoundException
      We're going to examine rows from the middle outward, searching alternately above and below the middle, and farther out each time. rowStep is the number of rows between each successive attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then middle + rowStep, then middle - (2 * rowStep), etc. rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily decided that moving up and down by about 1/16 of the image is pretty good; we try more of the image if "trying harder".
      Parameters:
      image - The image to decode
      hints - Any hints that were requested
      Returns:
      The contents of the decoded barcode
      Throws:
      NotFoundException - Any spontaneous errors which occur

    • 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