예제 #1
0
  /**
   * @return the 3 best {@link FinderPattern}s from our list of candidates. The "best" are those
   *     that have been detected at least {@link #CENTER_QUORUM} times, and whose module size
   *     differs from the average among those patterns the least
   * @throws NotFoundException if 3 such finder patterns do not exist
   */
  private FinderPattern[][] selectBestPatterns() throws NotFoundException {
    Vector possibleCenters = getPossibleCenters();
    int size = possibleCenters.size();

    if (size < 3) {
      // Couldn't find enough finder patterns
      throw NotFoundException.getNotFoundInstance();
    }

    /*
     * Begin HE modifications to safely detect multiple codes of equal size
     */
    if (size == 3) {
      return new FinderPattern[][] {
        new FinderPattern[] {
          (FinderPattern) possibleCenters.elementAt(0),
          (FinderPattern) possibleCenters.elementAt(1),
          (FinderPattern) possibleCenters.elementAt(2)
        }
      };
    }

    // Sort by estimated module size to speed up the upcoming checks
    Collections.insertionSort(possibleCenters, new ModuleSizeComparator());

    /*
     * Now lets start: build a list of tuples of three finder locations that
     * - feature similar module sizes - are placed in a distance so the
     * estimated module count is within the QR specification - have similar
     * distance between upper left/right and left top/bottom finder patterns
     * - form a triangle with 90° angle (checked by comparing top
     * right/bottom left distance with pythagoras)
     *
     * Note: we allow each point to be used for more than one code region:
     * this might seem counterintuitive at first, but the performance
     * penalty is not that big. At this point, we cannot make a good quality
     * decision whether the three finders actually represent a QR code, or
     * are just by chance layouted so it looks like there might be a QR code
     * there. So, if the layout seems right, lets have the decoder try to
     * decode.
     */

    Vector results = new Vector(); // holder for the results

    for (int i1 = 0; i1 < (size - 2); i1++) {
      FinderPattern p1 = (FinderPattern) possibleCenters.elementAt(i1);
      if (p1 == null) {
        continue;
      }

      for (int i2 = i1 + 1; i2 < (size - 1); i2++) {
        FinderPattern p2 = (FinderPattern) possibleCenters.elementAt(i2);
        if (p2 == null) {
          continue;
        }

        // Compare the expected module sizes; if they are really off,
        // skip
        float vModSize12 =
            (p1.getEstimatedModuleSize() - p2.getEstimatedModuleSize())
                / (Math.min(p1.getEstimatedModuleSize(), p2.getEstimatedModuleSize()));
        float vModSize12A = Math.abs(p1.getEstimatedModuleSize() - p2.getEstimatedModuleSize());
        if (vModSize12A > DIFF_MODSIZE_CUTOFF && vModSize12 >= DIFF_MODSIZE_CUTOFF_PERCENT) {
          // break, since elements are ordered by the module size
          // deviation there cannot be
          // any more interesting elements for the given p1.
          break;
        }

        for (int i3 = i2 + 1; i3 < size; i3++) {
          FinderPattern p3 = (FinderPattern) possibleCenters.elementAt(i3);
          if (p3 == null) {
            continue;
          }

          // Compare the expected module sizes; if they are really
          // off, skip
          float vModSize23 =
              (p2.getEstimatedModuleSize() - p3.getEstimatedModuleSize())
                  / (Math.min(p2.getEstimatedModuleSize(), p3.getEstimatedModuleSize()));
          float vModSize23A = Math.abs(p2.getEstimatedModuleSize() - p3.getEstimatedModuleSize());
          if (vModSize23A > DIFF_MODSIZE_CUTOFF && vModSize23 >= DIFF_MODSIZE_CUTOFF_PERCENT) {
            // break, since elements are ordered by the module size
            // deviation there cannot be
            // any more interesting elements for the given p1.
            break;
          }

          FinderPattern[] test = {p1, p2, p3};
          ResultPoint.orderBestPatterns(test);

          // Calculate the distances: a = topleft-bottomleft,
          // b=topleft-topright, c = diagonal
          FinderPatternInfo info = new FinderPatternInfo(test);
          float dA = ResultPoint.distance(info.getTopLeft(), info.getBottomLeft());
          float dC = ResultPoint.distance(info.getTopRight(), info.getBottomLeft());
          float dB = ResultPoint.distance(info.getTopLeft(), info.getTopRight());

          // Check the sizes
          float estimatedModuleCount = ((dA + dB) / p1.getEstimatedModuleSize()) / 2;
          if (estimatedModuleCount > MAX_MODULE_COUNT_PER_EDGE
              || estimatedModuleCount < MIN_MODULE_COUNT_PER_EDGE) {
            continue;
          }

          // Calculate the difference of the edge lengths in percent
          float vABBC = Math.abs(((dA - dB) / Math.min(dA, dB)));
          if (vABBC >= 0.1f) {
            continue;
          }

          // Calculate the diagonal length by assuming a 90° angle at
          // topleft
          float dCpy = (float) Math.sqrt(dA * dA + dB * dB);
          // Compare to the real distance in %
          float vPyC = Math.abs(((dC - dCpy) / Math.min(dC, dCpy)));

          if (vPyC >= 0.1f) {
            continue;
          }

          // All tests passed!
          results.addElement(test);
        } // end iterate p3
      } // end iterate p2
    } // end iterate p1

    if (!results.isEmpty()) {
      FinderPattern[][] resultArray = new FinderPattern[results.size()][];
      for (int i = 0; i < results.size(); i++) {
        resultArray[i] = (FinderPattern[]) results.elementAt(i);
      }
      return resultArray;
    }

    // Nothing found!
    throw NotFoundException.getNotFoundInstance();
  }