content: /*
   * Copyright 2007 ZXing authors
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.ailiwean.core.zxing.core.qrcode.detector;
  
  
  import com.ailiwean.core.zxing.core.NotFoundException;
  import com.ailiwean.core.zxing.core.ResultPointCallback;
  import com.ailiwean.core.zxing.core.common.BitMatrix;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * <p>This class attempts to find alignment patterns in a QR Code. Alignment patterns look like finder
   * patterns but are smaller and appear at regular intervals throughout the image.</p>
   *
   * <p>At the moment this only looks for the bottom-right alignment pattern.</p>
   *
   * <p>This is mostly a simplified copy of {@link FinderPatternFinder}. It is copied,
   * pasted and stripped down here for maximum performance but does unfortunately duplicate
   * some code.</p>
   *
   * <p>This class is thread-safe but not reentrant. Each thread must allocate its own object.</p>
   *
   * @author Sean Owen
   */
  final class AlignmentPatternFinder {
  
    private final BitMatrix image;
    private final List<AlignmentPattern> possibleCenters;
    private final int startX;
    private final int startY;
    private final int width;
    private final int height;
    private final float moduleSize;
    private final int[] crossCheckStateCount;
    private final ResultPointCallback resultPointCallback;
  
    /**
     * <p>Creates a finder that will look in a portion of the whole image.</p>
     *
     * @param image image to search
     * @param startX left column from which to start searching
     * @param startY top row from which to start searching
     * @param width width of region to search
     * @param height height of region to search
     * @param moduleSize estimated module size so far
     */
    AlignmentPatternFinder(BitMatrix image,
                           int startX,
                           int startY,
                           int width,
                           int height,
                           float moduleSize,
                           ResultPointCallback resultPointCallback) {
      this.image = image;
      this.possibleCenters = new ArrayList<>(5);
      this.startX = startX;
      this.startY = startY;
      this.width = width;
      this.height = height;
      this.moduleSize = moduleSize;
      this.crossCheckStateCount = new int[3];
      this.resultPointCallback = resultPointCallback;
    }
  
    /**
     * <p>This method attempts to find the bottom-right alignment pattern in the image. It is a bit messy since
     * it's pretty performance-critical and so is written to be fast foremost.</p>
     *
     * @return {@link AlignmentPattern} if found
     * @throws NotFoundException if not found
     */
    AlignmentPattern find() throws NotFoundException {
      int startX = this.startX;
      int height = this.height;
      int maxJ = startX + width;
      int middleI = startY + (height / 2);
      // We are looking for black/white/black modules in 1:1:1 ratio;
      // this tracks the number of black/white/black modules seen so far
      int[] stateCount = new int[3];
      for (int iGen = 0; iGen < height; iGen++) {
        // Search from middle outwards
        int i = middleI + ((iGen & 0x01) == 0 ? (iGen + 1) / 2 : -((iGen + 1) / 2));
        stateCount[0] = 0;
        stateCount[1] = 0;
        stateCount[2] = 0;
        int j = startX;
        // Burn off leading white pixels before anything else; if we start in the middle of
        // a white run, it doesn't make sense to count its length, since we don't know if the
        // white run continued to the left of the start point
        while (j < maxJ && !image.get(j, i)) {
          j++;
        }
        int currentState = 0;
        while (j < maxJ) {
          if (image.get(j, i)) {
            // Black pixel
            if (currentState == 1) { // Counting black pixels
              stateCount[1]++;
            } else { // Counting white pixels
              if (currentState == 2) { // A winner?
                if (foundPatternCross(stateCount)) { // Yes
                  AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, j);
                  if (confirmed != null) {
                    return confirmed;
                  }
                }
                stateCount[0] = stateCount[2];
                stateCount[1] = 1;
                stateCount[2] = 0;
                currentState = 1;
              } else {
                stateCount[++currentState]++;
              }
            }
          } else { // White pixel
            if (currentState == 1) { // Counting black pixels
              currentState++;
            }
            stateCount[currentState]++;
          }
          j++;
        }
        if (foundPatternCross(stateCount)) {
          AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, maxJ);
          if (confirmed != null) {
            return confirmed;
          }
        }
  
      }
  
      // Hmm, nothing we saw was observed and confirmed twice. If we had
      // any guess at all, return it.
      if (!possibleCenters.isEmpty()) {
        return possibleCenters.get(0);
      }
  
      throw NotFoundException.getNotFoundInstance();
    }
  
    /**
     * Given a count of black/white/black pixels just seen and an end position,
     * figures the location of the center of this black/white/black run.
     */
    private static float centerFromEnd(int[] stateCount, int end) {
      return (end - stateCount[2]) - stateCount[1] / 2.0f;
    }
  
    /**
     * @param stateCount count of black/white/black pixels just read
     * @return true iff the proportions of the counts is close enough to the 1/1/1 ratios
     *         used by alignment patterns to be considered a match
     */
    private boolean foundPatternCross(int[] stateCount) {
      float moduleSize = this.moduleSize;
      float maxVariance = moduleSize / 2.0f;
      for (int i = 0; i < 3; i++) {
        if (Math.abs(moduleSize - stateCount[i]) >= maxVariance) {
          return false;
        }
      }
      return true;
    }
  
    /**
     * <p>After a horizontal scan finds a potential alignment pattern, this method
     * "cross-checks" by scanning down vertically through the center of the possible
     * alignment pattern to see if the same proportion is detected.</p>
     *
     * @param startI row where an alignment pattern was detected
     * @param centerJ center of the section that appears to cross an alignment pattern
     * @param maxCount maximum reasonable number of modules that should be
     * observed in any reading state, based on the results of the horizontal scan
     * @return vertical center of alignment pattern, or {@link Float#NaN} if not found
     */
    private float crossCheckVertical(int startI, int centerJ, int maxCount,
        int originalStateCountTotal) {
      BitMatrix image = this.image;
  
      int maxI = image.getHeight();
      int[] stateCount = crossCheckStateCount;
      stateCount[0] = 0;
      stateCount[1] = 0;
      stateCount[2] = 0;
  
      // Start counting up from center
      int i = startI;
      while (i >= 0 && image.get(centerJ, i) && stateCount[1] <= maxCount) {
        stateCount[1]++;
        i--;
      }
      // If already too many modules in this state or ran off the edge:
      if (i < 0 || stateCount[1] > maxCount) {
        return Float.NaN;
      }
      while (i >= 0 && !image.get(centerJ, i) && stateCount[0] <= maxCount) {
        stateCount[0]++;
        i--;
      }
      if (stateCount[0] > maxCount) {
        return Float.NaN;
      }
  
      // Now also count down from center
      i = startI + 1;
      while (i < maxI && image.get(centerJ, i) && stateCount[1] <= maxCount) {
        stateCount[1]++;
        i++;
      }
      if (i == maxI || stateCount[1] > maxCount) {
        return Float.NaN;
      }
      while (i < maxI && !image.get(centerJ, i) && stateCount[2] <= maxCount) {
        stateCount[2]++;
        i++;
      }
      if (stateCount[2] > maxCount) {
        return Float.NaN;
      }
  
      int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
      if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal) {
        return Float.NaN;
      }
  
      return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : Float.NaN;
    }
  
    /**
     * <p>This is called when a horizontal scan finds a possible alignment pattern. It will
     * cross check with a vertical scan, and if successful, will see if this pattern had been
     * found on a previous horizontal scan. If so, we consider it confirmed and conclude we have
     * found the alignment pattern.</p>
     *
     * @param stateCount reading state module counts from horizontal scan
     * @param i row where alignment pattern may be found
     * @param j end of possible alignment pattern in row
     * @return {@link AlignmentPattern} if we have found the same pattern twice, or null if not
     */
    private AlignmentPattern handlePossibleCenter(int[] stateCount, int i, int j) {
      int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
      float centerJ = centerFromEnd(stateCount, j);
      float centerI = crossCheckVertical(i, (int) centerJ, 2 * stateCount[1], stateCountTotal);
      if (!Float.isNaN(centerI)) {
        float estimatedModuleSize = (stateCount[0] + stateCount[1] + stateCount[2]) / 3.0f;
        for (AlignmentPattern center : possibleCenters) {
          // Look for about the same center and module size:
          if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {
            return center.combineEstimate(centerI, centerJ, estimatedModuleSize);
          }
        }
        // Hadn't found this before; save it
        AlignmentPattern point = new AlignmentPattern(centerJ, centerI, estimatedModuleSize);
        possibleCenters.add(point);
        if (resultPointCallback != null) {
          resultPointCallback.foundPossibleResultPoint(point);
        }
      }
      return null;
    }
  
  }
  