Class FinderPatternFinder

java.lang.Object
com.google.zxing.qrcode.detector.FinderPatternFinder
Direct Known Subclasses:
MultiFinderPatternFinder

public class FinderPatternFinder extends Object

This class attempts to find finder patterns in a QR Code. Finder patterns are the square markers at three corners of a QR Code.

This class is thread-safe but not reentrant. Each thread must allocate its own object.

Author:
Sean Owen
  • Field Details

  • Constructor Details

    • FinderPatternFinder

      public FinderPatternFinder(BitMatrix image)

      Creates a finder that will search the image for three finder patterns.

      Parameters:
      image - image to search
    • FinderPatternFinder

      public FinderPatternFinder(BitMatrix image, ResultPointCallback resultPointCallback)
  • Method Details

    • getImage

      protected final BitMatrix getImage()
    • getPossibleCenters

      protected final List<FinderPattern> getPossibleCenters()
    • foundPatternCross

      protected static boolean foundPatternCross(int[] stateCount)
      Parameters:
      stateCount - count of black/white/black/white/black pixels just read
      Returns:
      true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios used by finder patterns to be considered a match
    • foundPatternDiagonal

      protected static boolean foundPatternDiagonal(int[] stateCount)
      Parameters:
      stateCount - count of black/white/black/white/black pixels just read
      Returns:
      true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios used by finder patterns to be considered a match
    • clearCounts

      @Deprecated protected final void clearCounts(int[] counts)
      Deprecated.
    • shiftCounts2

      @Deprecated protected final void shiftCounts2(int[] stateCount)
      Deprecated.
    • doClearCounts

      protected static void doClearCounts(int[] counts)
    • doShiftCounts2

      protected static void doShiftCounts2(int[] stateCount)
    • handlePossibleCenter

      @Deprecated protected final boolean handlePossibleCenter(int[] stateCount, int i, int j, boolean pureBarcode)
      Deprecated.
      only exists for backwards compatibility
      Parameters:
      stateCount - reading state module counts from horizontal scan
      i - row where finder pattern may be found
      j - end of possible finder pattern in row
      pureBarcode - ignored
      Returns:
      true if a finder pattern candidate was found this time
      See Also:
    • handlePossibleCenter

      protected final boolean handlePossibleCenter(int[] stateCount, int i, int j)

      This is called when a horizontal scan finds a possible alignment pattern. It will cross check with a vertical scan, and if successful, will, ah, cross-cross-check with another horizontal scan. This is needed primarily to locate the real horizontal center of the pattern in cases of extreme skew. And then we cross-cross-cross check with another diagonal scan.

      If that succeeds the finder pattern location is added to a list that tracks the number of times each location has been nearly-matched as a finder pattern. Each additional find is more evidence that the location is in fact a finder pattern center

      Parameters:
      stateCount - reading state module counts from horizontal scan
      i - row where finder pattern may be found
      j - end of possible finder pattern in row
      Returns:
      true if a finder pattern candidate was found this time