FinderPatternFinder.php

<?php
/*
* 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.
*/

namespace Zxing\Qrcode\Detector;

use Zxing\BinaryBitmap;
use Zxing\Common\BitMatrix;
use Zxing\NotFoundException;
use Zxing\ResultPoint;

/**
 * <p>This class attempts to find finder patterns in a QR Code. Finder patterns are the square
 * markers at three corners of a QR Code.</p>
 *
 * <p>This class is thread-safe but not reentrant. Each thread must allocate its own object.
 *
 * @author Sean Owen
 */
class FinderPatternFinder
{
    protected static $MIN_SKIP = 3;
    protected static $MAX_MODULES = 57; // 1 pixel/module times 3 modules/center
    private static $CENTER_QUORUM = 2; // support up to version 10 for mobile clients
    private $image;
    private $average;
    private $possibleCenters; //private final List<FinderPattern> possibleCenters;
    private $hasSkipped = false;
    private $crossCheckStateCount;
    private $resultPointCallback;

    /**
     * <p>Creates a finder that will search the image for three finder patterns.</p>
     *
     * @param BitMatrix $image image to search
     */
    public function __construct($image, $resultPointCallback = null)
    {
        $this->image = $image;


        $this->possibleCenters      = [];//new ArrayList<>();
        $this->crossCheckStateCount = fill_array(0, 5, 0);
        $this->resultPointCallback  = $resultPointCallback;
    }

    final public function find($hints)
    {/*final FinderPatternInfo find(Map<DecodeHintType,?> hints) throws NotFoundException {*/
        $tryHarder = true;//$hints != null && $hints['TRY_HARDER'];
        $pureBarcode = $hints != null && $hints['PURE_BARCODE'];
        $maxI        = $this->image->getHeight();
        $maxJ        = $this->image->getWidth();
        // We are looking for black/white/black/white/black modules in
        // 1:1:3:1:1 ratio; this tracks the number of such modules seen so far

        // Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
        // image, and then account for the center being 3 modules in size. This gives the smallest
        // number of pixels the center could be, so skip this often. When trying harder, look for all
        // QR versions regardless of how dense they are.
        $iSkip = (int)((3 * $maxI) / (4 * self::$MAX_MODULES));
        if ($iSkip < self::$MIN_SKIP || $tryHarder) {
            $iSkip = self::$MIN_SKIP;
        }

        $done       = false;
        $stateCount = [];
        for ($i = $iSkip - 1; $i < $maxI && !$done; $i += $iSkip) {
            // Get a row of black/white values
            $stateCount[0] = 0;
            $stateCount[1] = 0;
            $stateCount[2] = 0;
            $stateCount[3] = 0;
            $stateCount[4] = 0;
            $currentState  = 0;
            for ($j = 0; $j < $maxJ; $j++) {
                if ($this->image->get($j, $i)) {
                    // Black pixel
                    if (($currentState & 1) == 1) { // Counting white pixels
                        $currentState++;
                    }
                    $stateCount[$currentState]++;
                } else { // White pixel
                    if (($currentState & 1) == 0) { // Counting black pixels
                        if ($currentState == 4) { // A winner?
                            if (self::foundPatternCross($stateCount)) { // Yes
                                $confirmed = $this->handlePossibleCenter($stateCount, $i, $j, $pureBarcode);
                                if ($confirmed) {
                                    // Start examining every other line. Checking each line turned out to be too
                                    // expensive and didn't improve performance.
                                    $iSkip = 3;
                                    if ($this->hasSkipped) {
                                        $done = $this->haveMultiplyConfirmedCenters();
                                    } else {
                                        $rowSkip = $this->findRowSkip();
                                        if ($rowSkip > $stateCount[2]) {
                                            // Skip rows between row of lower confirmed center
                                            // and top of presumed third confirmed center
                                            // but back up a bit to get a full chance of detecting
                                            // it, entire width of center of finder pattern

                                            // Skip by rowSkip, but back off by $stateCount[2] (size of last center
                                            // of pattern we saw) to be conservative, and also back off by iSkip which
                                            // is about to be re-added
                                            $i += $rowSkip - $stateCount[2] - $iSkip;
                                            $j = $maxJ - 1;
                                        }
                                    }
                                } else {
                                    $stateCount[0] = $stateCount[2];
                                    $stateCount[1] = $stateCount[3];
                                    $stateCount[2] = $stateCount[4];
                                    $stateCount[3] = 1;
                                    $stateCount[4] = 0;
                                    $currentState  = 3;
                                    continue;
                                }
                                // Clear state to start looking again
                                $currentState  = 0;
                                $stateCount[0] = 0;
                                $stateCount[1] = 0;
                                $stateCount[2] = 0;
                                $stateCount[3] = 0;
                                $stateCount[4] = 0;
                            } else { // No, shift counts back by two
                                $stateCount[0] = $stateCount[2];
                                $stateCount[1] = $stateCount[3];
                                $stateCount[2] = $stateCount[4];
                                $stateCount[3] = 1;
                                $stateCount[4] = 0;
                                $currentState  = 3;
                            }
                        } else {
                            $stateCount[++$currentState]++;
                        }
                    } else { // Counting white pixels
                        $stateCount[$currentState]++;
                    }
                }
            }
            if (self::foundPatternCross($stateCount)) {
                $confirmed = $this->handlePossibleCenter($stateCount, $i, $maxJ, $pureBarcode);
                if ($confirmed) {
                    $iSkip = $stateCount[0];
                    if ($this->hasSkipped) {
                        // Found a third one
                        $done = $this->haveMultiplyConfirmedCenters();
                    }
                }
            }
        }

        $patternInfo = $this->selectBestPatterns();
        $patternInfo = ResultPoint::orderBestPatterns($patternInfo);

        return new FinderPatternInfo($patternInfo);
    }

    /**
     * @param $stateCount ; count of black/white/black/white/black pixels just read
     *
     * @return true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios
     *         used by finder patterns to be considered a match
     */
    protected static function foundPatternCross($stateCount)
    {
        $totalModuleSize = 0;
        for ($i = 0; $i < 5; $i++) {
            $count = $stateCount[$i];
            if ($count == 0) {
                return false;
            }
            $totalModuleSize += $count;
        }
        if ($totalModuleSize < 7) {
            return false;
        }
        $moduleSize  = $totalModuleSize / 7.0;
        $maxVariance = $moduleSize / 2.0;

        // Allow less than 50% variance from 1-1-3-1-1 proportions
        return
            abs($moduleSize - $stateCount[0]) < $maxVariance &&
            abs($moduleSize - $stateCount[1]) < $maxVariance &&
            abs(3.0 * $moduleSize - $stateCount[2]) < 3 * $maxVariance &&
            abs($moduleSize - $stateCount[3]) < $maxVariance &&
            abs($moduleSize - $stateCount[4]) < $maxVariance;
    }

    /**
     * <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, 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.</p>
     *
     * <p>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
     *
     * @param $stateCount reading state module counts from horizontal scan
     * @param i           row where finder pattern may be found
     * @param j           end of possible finder pattern in row
     * @param pureBarcode true if in "pure barcode" mode
     *
     * @return true if a finder pattern candidate was found this time
     */
    protected final function handlePossibleCenter($stateCount, $i, $j, $pureBarcode)
    {
        $stateCountTotal = $stateCount[0] + $stateCount[1] + $stateCount[2] + $stateCount[3] +
            $stateCount[4];
        $centerJ         = $this->centerFromEnd($stateCount, $j);
        $centerI         = $this->crossCheckVertical($i, (int)($centerJ), $stateCount[2], $stateCountTotal);
        if (!is_nan($centerI)) {
            // Re-cross check
            $centerJ = $this->crossCheckHorizontal((int)($centerJ), (int)($centerI), $stateCount[2], $stateCountTotal);
            if (!is_nan($centerJ) &&
                (!$pureBarcode || $this->crossCheckDiagonal((int)($centerI), (int)($centerJ), $stateCount[2], $stateCountTotal))
            ) {
                $estimatedModuleSize = (float)$stateCountTotal / 7.0;
                $found               = false;
                for ($index = 0; $index < count($this->possibleCenters); $index++) {
                    $center = $this->possibleCenters[$index];
                    // Look for about the same center and module size:
                    if ($center->aboutEquals($estimatedModuleSize, $centerI, $centerJ)) {
                        $this->possibleCenters[$index] = $center->combineEstimate($centerI, $centerJ, $estimatedModuleSize);
                        $found                         = true;
                        break;
                    }
                }
                if (!$found) {
                    $point                   = new FinderPattern($centerJ, $centerI, $estimatedModuleSize);
                    $this->possibleCenters[] = $point;
                    if ($this->resultPointCallback != null) {
                        $this->resultPointCallback->foundPossibleResultPoint($point);
                    }
                }

                return true;
            }
        }

        return false;
    }

    /**
     * Given a count of black/white/black/white/black pixels just seen and an end position,
     * figures the location of the center of this run.
     */
    private static function centerFromEnd($stateCount, $end)
    {
        return (float)($end - $stateCount[4] - $stateCount[3]) - $stateCount[2] / 2.0;
    }

    /**
     * <p>After a horizontal scan finds a potential finder pattern, this method
     * "cross-checks" by scanning down vertically through the center of the possible
     * finder pattern to see if the same proportion is detected.</p>
     *
     * @param $startI   ;  row where a finder pattern was detected
     * @param centerJ   ; center of the section that appears to cross a finder pattern
     * @param $maxCount ; maximum reasonable number of modules that should be
     *                  observed in any reading state, based on the results of the horizontal scan
     *
     * @return vertical center of finder pattern, or {@link Float#NaN} if not found
     */
    private function crossCheckVertical($startI, $centerJ, $maxCount,
                                        $originalStateCountTotal)
    {
        $image = $this->image;

        $maxI       = $image->getHeight();
        $stateCount = $this->getCrossCheckStateCount();

        // Start counting up from center
        $i = $startI;
        while ($i >= 0 && $image->get($centerJ, $i)) {
            $stateCount[2]++;
            $i--;
        }
        if ($i < 0) {
            return NAN;
        }
        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] > $maxCount) {
            return NAN;
        }
        while ($i >= 0 && $image->get($centerJ, $i) && $stateCount[0] <= $maxCount) {
            $stateCount[0]++;
            $i--;
        }
        if ($stateCount[0] > $maxCount) {
            return NAN;
        }

        // Now also count down from center
        $i = $startI + 1;
        while ($i < $maxI && $image->get($centerJ, $i)) {
            $stateCount[2]++;
            $i++;
        }
        if ($i == $maxI) {
            return NAN;
        }
        while ($i < $maxI && !$image->get($centerJ, $i) && $stateCount[3] < $maxCount) {
            $stateCount[3]++;
            $i++;
        }
        if ($i == $maxI || $stateCount[3] >= $maxCount) {
            return NAN;
        }
        while ($i < $maxI && $image->get($centerJ, $i) && $stateCount[4] < $maxCount) {
            $stateCount[4]++;
            $i++;
        }
        if ($stateCount[4] >= $maxCount) {
            return NAN;
        }

        // If we found a finder-pattern-like section, but its size is more than 40% different than
        // the original, assume it's a false positive
        $stateCountTotal = $stateCount[0] + $stateCount[1] + $stateCount[2] + $stateCount[3] +
            $stateCount[4];
        if (5 * abs($stateCountTotal - $originalStateCountTotal) >= 2 * $originalStateCountTotal) {
            return NAN;
        }

        return self::foundPatternCross($stateCount) ? $this->centerFromEnd($stateCount, $i) : NAN;
    }

    private function getCrossCheckStateCount()
    {
        $this->crossCheckStateCount[0] = 0;
        $this->crossCheckStateCount[1] = 0;
        $this->crossCheckStateCount[2] = 0;
        $this->crossCheckStateCount[3] = 0;
        $this->crossCheckStateCount[4] = 0;

        return $this->crossCheckStateCount;
    }

    /**
     * <p>Like {@link #crossCheckVertical(int, int, int, int)}, and in fact is basically identical,
     * except it reads horizontally instead of vertically. This is used to cross-cross
     * check a vertical cross check and locate the real center of the alignment pattern.</p>
     */
    private function crossCheckHorizontal($startJ, $centerI, $maxCount,
                                          $originalStateCountTotal)
    {
        $image = $this->image;

        $maxJ       = $this->image->getWidth();
        $stateCount = $this->getCrossCheckStateCount();

        $j = $startJ;
        while ($j >= 0 && $image->get($j, $centerI)) {
            $stateCount[2]++;
            $j--;
        }
        if ($j < 0) {
            return NAN;
        }
        while ($j >= 0 && !$image->get($j, $centerI) && $stateCount[1] <= $maxCount) {
            $stateCount[1]++;
            $j--;
        }
        if ($j < 0 || $stateCount[1] > $maxCount) {
            return NAN;
        }
        while ($j >= 0 && $image->get($j, $centerI) && $stateCount[0] <= $maxCount) {
            $stateCount[0]++;
            $j--;
        }
        if ($stateCount[0] > $maxCount) {
            return NAN;
        }

        $j = $startJ + 1;
        while ($j < $maxJ && $image->get($j, $centerI)) {
            $stateCount[2]++;
            $j++;
        }
        if ($j == $maxJ) {
            return NAN;
        }
        while ($j < $maxJ && !$image->get($j, $centerI) && $stateCount[3] < $maxCount) {
            $stateCount[3]++;
            $j++;
        }
        if ($j == $maxJ || $stateCount[3] >= $maxCount) {
            return NAN;
        }
        while ($j < $maxJ && $this->image->get($j, $centerI) && $stateCount[4] < $maxCount) {
            $stateCount[4]++;
            $j++;
        }
        if ($stateCount[4] >= $maxCount) {
            return NAN;
        }

        // If we found a finder-pattern-like section, but its size is significantly different than
        // the original, assume it's a false positive
        $stateCountTotal = $stateCount[0] + $stateCount[1] + $stateCount[2] + $stateCount[3] +
            $stateCount[4];
        if (5 * abs($stateCountTotal - $originalStateCountTotal) >= $originalStateCountTotal) {
            return NAN;
        }

        return $this->foundPatternCross($stateCount) ? $this->centerFromEnd($stateCount, $j) : NAN;
    }

    /**
     * After a vertical and horizontal scan finds a potential finder pattern, this method
     * "cross-cross-cross-checks" by scanning down diagonally through the center of the possible
     * finder pattern to see if the same proportion is detected.
     *
     * @param $startI                 ;  row where a finder pattern was detected
     * @param centerJ                 ; center of the section that appears to cross a finder pattern
     * @param $maxCount               ; maximum reasonable number of modules that should be
     *                                observed in any reading state, based on the results of the horizontal scan
     * @param originalStateCountTotal ; The original state count total.
     *
     * @return true if proportions are withing expected limits
     */
    private function crossCheckDiagonal($startI, $centerJ, $maxCount, $originalStateCountTotal)
    {
        $stateCount = $this->getCrossCheckStateCount();

        // Start counting up, left from center finding black center mass
        $i       = 0;
        $startI  = (int)($startI);
        $centerJ = (int)($centerJ);
        while ($startI >= $i && $centerJ >= $i && $this->image->get($centerJ - $i, $startI - $i)) {
            $stateCount[2]++;
            $i++;
        }

        if ($startI < $i || $centerJ < $i) {
            return false;
        }

        // Continue up, left finding white space
        while ($startI >= $i && $centerJ >= $i && !$this->image->get($centerJ - $i, $startI - $i) &&
            $stateCount[1] <= $maxCount) {
            $stateCount[1]++;
            $i++;
        }

        // If already too many modules in this state or ran off the edge:
        if ($startI < $i || $centerJ < $i || $stateCount[1] > $maxCount) {
            return false;
        }

        // Continue up, left finding black border
        while ($startI >= $i && $centerJ >= $i && $this->image->get($centerJ - $i, $startI - $i) &&
            $stateCount[0] <= $maxCount) {
            $stateCount[0]++;
            $i++;
        }
        if ($stateCount[0] > $maxCount) {
            return false;
        }

        $maxI = $this->image->getHeight();
        $maxJ = $this->image->getWidth();

        // Now also count down, right from center
        $i = 1;
        while ($startI + $i < $maxI && $centerJ + $i < $maxJ && $this->image->get($centerJ + $i, $startI + $i)) {
            $stateCount[2]++;
            $i++;
        }

        // Ran off the edge?
        if ($startI + $i >= $maxI || $centerJ + $i >= $maxJ) {
            return false;
        }

        while ($startI + $i < $maxI && $centerJ + $i < $maxJ && !$this->image->get($centerJ + $i, $startI + $i) &&
            $stateCount[3] < $maxCount) {
            $stateCount[3]++;
            $i++;
        }

        if ($startI + $i >= $maxI || $centerJ + $i >= $maxJ || $stateCount[3] >= $maxCount) {
            return false;
        }

        while ($startI + $i < $maxI && $centerJ + $i < $maxJ && $this->image->get($centerJ + $i, $startI + $i) &&
            $stateCount[4] < $maxCount) {
            $stateCount[4]++;
            $i++;
        }

        if ($stateCount[4] >= $maxCount) {
            return false;
        }

        // If we found a finder-pattern-like section, but its size is more than 100% different than
        // the original, assume it's a false positive
        $stateCountTotal = $stateCount[0] + $stateCount[1] + $stateCount[2] + $stateCount[3] + $stateCount[4];

        return
            abs($stateCountTotal - $originalStateCountTotal) < 2 * $originalStateCountTotal &&
            self::foundPatternCross($stateCount);
    }

    /**
     * @return true iff we have found at least 3 finder patterns that have been detected
     *         at least {@link #CENTER_QUORUM} times each, and, the estimated module size of the
     *         candidates is "pretty similar"
     */
    private function haveMultiplyConfirmedCenters()
    {
        $confirmedCount  = 0;
        $totalModuleSize = 0.0;
        $max             = count($this->possibleCenters);
        foreach ($this->possibleCenters as $pattern) {
            if ($pattern->getCount() >= self::$CENTER_QUORUM) {
                $confirmedCount++;
                $totalModuleSize += $pattern->getEstimatedModuleSize();
            }
        }
        if ($confirmedCount < 3) {
            return false;
        }
        // OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
        // and that we need to keep looking. We detect this by asking if the estimated module sizes
        // vary too much. We arbitrarily say that when the total deviation from average exceeds
        // 5% of the total module size estimates, it's too much.
        $average        = $totalModuleSize / (float)$max;
        $totalDeviation = 0.0;
        foreach ($this->possibleCenters as $pattern) {
            $totalDeviation += abs($pattern->getEstimatedModuleSize() - $average);
        }

        return $totalDeviation <= 0.05 * $totalModuleSize;
    }

    /**
     * @return number of rows we could safely skip during scanning, based on the first
     *         two finder patterns that have been located. In some cases their position will
     *         allow us to infer that the third pattern must lie below a certain point farther
     *         down in the image.
     */
    private function findRowSkip()
    {
        $max = count($this->possibleCenters);
        if ($max <= 1) {
            return 0;
        }
        $firstConfirmedCenter = null;
        foreach ($this->possibleCenters as $center) {


            if ($center->getCount() >= self::$CENTER_QUORUM) {
                if ($firstConfirmedCenter == null) {
                    $firstConfirmedCenter = $center;
                } else {
                    // We have two confirmed centers
                    // How far down can we skip before resuming looking for the next
                    // pattern? In the worst case, only the difference between the
                    // difference in the x / y coordinates of the two centers.
                    // This is the case where you find top left last.
                    $this->hasSkipped = true;

                    return (int)((abs($firstConfirmedCenter->getX() - $center->getX()) -
                            abs($firstConfirmedCenter->getY() - $center->getY())) / 2);
                }
            }
        }

        return 0;
    }

    /**
     * @return array 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 function selectBestPatterns()
    {
        $startSize = count($this->possibleCenters);
        if ($startSize < 3) {
            // Couldn't find enough finder patterns
            throw new NotFoundException;
        }

        // Filter outlier possibilities whose module size is too different
        if ($startSize > 3) {
            // But we can only afford to do so if we have at least 4 possibilities to choose from
            $totalModuleSize = 0.0;
            $square          = 0.0;
            foreach ($this->possibleCenters as $center) {
                $size            = $center->getEstimatedModuleSize();
                $totalModuleSize += $size;
                $square          += $size * $size;
            }
            $this->average = $totalModuleSize / (float)$startSize;
            $stdDev        = (float)sqrt($square / $startSize - $this->average * $this->average);

            usort($this->possibleCenters, [$this, 'FurthestFromAverageComparator']);

            $limit = max(0.2 * $this->average, $stdDev);

            for ($i = 0; $i < count($this->possibleCenters) && count($this->possibleCenters) > 3; $i++) {
                $pattern = $this->possibleCenters[$i];
                if (abs($pattern->getEstimatedModuleSize() - $this->average) > $limit) {
                    unset($this->possibleCenters[$i]);//возможно что ключи меняются в java при вызове .remove(i) ???
                    $this->possibleCenters = array_values($this->possibleCenters);
                    $i--;
                }
            }
        }

        if (count($this->possibleCenters) > 3) {
            // Throw away all but those first size candidate points we found.

            $totalModuleSize = 0.0;
            foreach ($this->possibleCenters as $possibleCenter) {
                $totalModuleSize += $possibleCenter->getEstimatedModuleSize();
            }

            $this->average = $totalModuleSize / (float)count($this->possibleCenters);

            usort($this->possibleCenters, [$this, 'CenterComparator']);

            array_slice($this->possibleCenters, 3, count($this->possibleCenters) - 3);
        }

        return [$this->possibleCenters[0], $this->possibleCenters[1], $this->possibleCenters[2]];
    }

    /**
     * <p>Orders by furthest from average</p>
     */
    public function FurthestFromAverageComparator($center1, $center2)
    {

        $dA = abs($center2->getEstimatedModuleSize() - $this->average);
        $dB = abs($center1->getEstimatedModuleSize() - $this->average);
        if ($dA < $dB) {
            return -1;
        } elseif ($dA == $dB) {
            return 0;
        } else {
            return 1;
        }
    }

    public function CenterComparator($center1, $center2)
    {
        if ($center2->getCount() == $center1->getCount()) {
            $dA = abs($center2->getEstimatedModuleSize() - $this->average);
            $dB = abs($center1->getEstimatedModuleSize() - $this->average);
            if ($dA < $dB) {
                return 1;
            } elseif ($dA == $dB) {
                return 0;
            } else {
                return -1;
            }
        } else {
            return $center2->getCount() - $center1->getCount();
        }
    }

    protected final function getImage()
    {
        return $this->image;
    }
    /**
     * <p>Orders by {@link FinderPattern#getCount()}, descending.</p>
     */

    //@Override
    protected final function getPossibleCenters()
    { //List<FinderPattern> getPossibleCenters()
        return $this->possibleCenters;
    }
}