362 lines
11 KiB
PHP
362 lines
11 KiB
PHP
<?php
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/**
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* Class Detector
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*
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* @created 17.01.2021
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* @author ZXing Authors
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* @author Smiley <smiley@chillerlan.net>
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* @copyright 2021 Smiley
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* @license Apache-2.0
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*/
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namespace chillerlan\QRCode\Detector;
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use chillerlan\QRCode\Common\{LuminanceSourceInterface, Version};
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use chillerlan\QRCode\Decoder\{Binarizer, BitMatrix};
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use function abs, intdiv, is_nan, max, min, round;
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use const NAN;
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/**
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* Encapsulates logic that can detect a QR Code in an image, even if the QR Code
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* is rotated or skewed, or partially obscured.
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*
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* @author Sean Owen
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*/
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final class Detector{
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private BitMatrix $matrix;
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/** @var \chillerlan\QRCode\Detector\FinderPattern[] */
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private array $finderPatterns = [];
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/**
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* Detector constructor.
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*/
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public function __construct(LuminanceSourceInterface $source){
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$this->matrix = (new Binarizer($source))->getBlackMatrix();
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}
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/**
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* @return \chillerlan\QRCode\Detector\FinderPattern[]
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*/
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public function getFinderPatterns():array{
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return $this->finderPatterns;
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}
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/**
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* Detects a QR Code in an image.
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*/
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public function detect():BitMatrix{
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$this->finderPatterns = (new FinderPatternFinder($this->matrix))->find();
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[$bottomLeft, $topLeft, $topRight] = $this->finderPatterns;
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$moduleSize = $this->calculateModuleSize($topLeft, $topRight, $bottomLeft);
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$dimension = $this->computeDimension($topLeft, $topRight, $bottomLeft, $moduleSize);
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$provisionalVersion = new Version(intdiv(($dimension - 17), 4));
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$alignmentPattern = null;
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// Anything above version 1 has an alignment pattern
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if(!empty($provisionalVersion->getAlignmentPattern())){
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// Guess where a "bottom right" finder pattern would have been
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$bottomRightX = ($topRight->getX() - $topLeft->getX() + $bottomLeft->getX());
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$bottomRightY = ($topRight->getY() - $topLeft->getY() + $bottomLeft->getY());
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// Estimate that alignment pattern is closer by 3 modules
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// from "bottom right" to known top left location
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$correctionToTopLeft = (1.0 - 3.0 / (float)($provisionalVersion->getDimension() - 7));
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$estAlignmentX = (int)($topLeft->getX() + $correctionToTopLeft * ($bottomRightX - $topLeft->getX()));
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$estAlignmentY = (int)($topLeft->getY() + $correctionToTopLeft * ($bottomRightY - $topLeft->getY()));
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// Kind of arbitrary -- expand search radius before giving up
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for($i = 4; $i <= 16; $i <<= 1){//??????????
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$alignmentPattern = $this->findAlignmentInRegion($moduleSize, $estAlignmentX, $estAlignmentY, (float)$i);
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if($alignmentPattern !== null){
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break;
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}
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}
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// If we didn't find alignment pattern... well try anyway without it
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}
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$transform = $this->createTransform($topLeft, $topRight, $bottomLeft, $dimension, $alignmentPattern);
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return (new GridSampler)->sampleGrid($this->matrix, $dimension, $transform);
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}
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/**
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* Computes an average estimated module size based on estimated derived from the positions
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* of the three finder patterns.
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*
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* @throws \chillerlan\QRCode\Detector\QRCodeDetectorException
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*/
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private function calculateModuleSize(FinderPattern $topLeft, FinderPattern $topRight, FinderPattern $bottomLeft):float{
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// Take the average
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$moduleSize = ((
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$this->calculateModuleSizeOneWay($topLeft, $topRight) +
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$this->calculateModuleSizeOneWay($topLeft, $bottomLeft)
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) / 2.0);
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if($moduleSize < 1.0){
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throw new QRCodeDetectorException('module size < 1.0');
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}
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return $moduleSize;
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}
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/**
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* Estimates module size based on two finder patterns -- it uses
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* #sizeOfBlackWhiteBlackRunBothWays(int, int, int, int) to figure the
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* width of each, measuring along the axis between their centers.
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*/
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private function calculateModuleSizeOneWay(FinderPattern $a, FinderPattern $b):float{
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$moduleSizeEst1 = $this->sizeOfBlackWhiteBlackRunBothWays($a->getX(), $a->getY(), $b->getX(), $b->getY());
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$moduleSizeEst2 = $this->sizeOfBlackWhiteBlackRunBothWays($b->getX(), $b->getY(), $a->getX(), $a->getY());
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if(is_nan($moduleSizeEst1)){
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return ($moduleSizeEst2 / 7.0);
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}
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if(is_nan($moduleSizeEst2)){
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return ($moduleSizeEst1 / 7.0);
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}
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// Average them, and divide by 7 since we've counted the width of 3 black modules,
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// and 1 white and 1 black module on either side. Ergo, divide sum by 14.
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return (($moduleSizeEst1 + $moduleSizeEst2) / 14.0);
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}
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/**
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* See #sizeOfBlackWhiteBlackRun(int, int, int, int); computes the total width of
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* a finder pattern by looking for a black-white-black run from the center in the direction
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* of another po$(another finder pattern center), and in the opposite direction too.
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*
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* @noinspection DuplicatedCode
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*/
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private function sizeOfBlackWhiteBlackRunBothWays(float $fromX, float $fromY, float $toX, float $toY):float{
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$result = $this->sizeOfBlackWhiteBlackRun((int)$fromX, (int)$fromY, (int)$toX, (int)$toY);
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$dimension = $this->matrix->getSize();
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// Now count other way -- don't run off image though of course
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$scale = 1.0;
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$otherToX = ($fromX - ($toX - $fromX));
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if($otherToX < 0){
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$scale = ($fromX / ($fromX - $otherToX));
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$otherToX = 0;
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}
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elseif($otherToX >= $dimension){
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$scale = (($dimension - 1 - $fromX) / ($otherToX - $fromX));
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$otherToX = ($dimension - 1);
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}
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$otherToY = (int)($fromY - ($toY - $fromY) * $scale);
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$scale = 1.0;
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if($otherToY < 0){
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$scale = ($fromY / ($fromY - $otherToY));
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$otherToY = 0;
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}
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elseif($otherToY >= $dimension){
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$scale = (($dimension - 1 - $fromY) / ($otherToY - $fromY));
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$otherToY = ($dimension - 1);
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}
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$otherToX = (int)($fromX + ($otherToX - $fromX) * $scale);
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$result += $this->sizeOfBlackWhiteBlackRun((int)$fromX, (int)$fromY, $otherToX, $otherToY);
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// Middle pixel is double-counted this way; subtract 1
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return ($result - 1.0);
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}
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/**
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* This method traces a line from a po$in the image, in the direction towards another point.
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* It begins in a black region, and keeps going until it finds white, then black, then white again.
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* It reports the distance from the start to this point.
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*
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* This is used when figuring out how wide a finder pattern is, when the finder pattern
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* may be skewed or rotated.
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*/
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private function sizeOfBlackWhiteBlackRun(int $fromX, int $fromY, int $toX, int $toY):float{
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// Mild variant of Bresenham's algorithm;
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// @see https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm
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$steep = abs($toY - $fromY) > abs($toX - $fromX);
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if($steep){
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$temp = $fromX;
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$fromX = $fromY;
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$fromY = $temp;
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$temp = $toX;
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$toX = $toY;
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$toY = $temp;
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}
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$dx = abs($toX - $fromX);
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$dy = abs($toY - $fromY);
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$error = (-$dx / 2);
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$xstep = (($fromX < $toX) ? 1 : -1);
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$ystep = (($fromY < $toY) ? 1 : -1);
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// In black pixels, looking for white, first or second time.
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$state = 0;
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// Loop up until x == toX, but not beyond
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$xLimit = ($toX + $xstep);
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for($x = $fromX, $y = $fromY; $x !== $xLimit; $x += $xstep){
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$realX = ($steep) ? $y : $x;
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$realY = ($steep) ? $x : $y;
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// Does current pixel mean we have moved white to black or vice versa?
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// Scanning black in state 0,2 and white in state 1, so if we find the wrong
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// color, advance to next state or end if we are in state 2 already
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if(($state === 1) === $this->matrix->check($realX, $realY)){
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if($state === 2){
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return FinderPattern::distance($x, $y, $fromX, $fromY);
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}
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$state++;
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}
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$error += $dy;
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if($error > 0){
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if($y === $toY){
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break;
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}
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$y += $ystep;
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$error -= $dx;
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}
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}
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// Found black-white-black; give the benefit of the doubt that the next pixel outside the image
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// is "white" so this last po$at (toX+xStep,toY) is the right ending. This is really a
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// small approximation; (toX+xStep,toY+yStep) might be really correct. Ignore this.
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if($state === 2){
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return FinderPattern::distance(($toX + $xstep), $toY, $fromX, $fromY);
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}
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// else we didn't find even black-white-black; no estimate is really possible
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return NAN;
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}
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/**
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* Computes the dimension (number of modules on a size) of the QR Code based on the position
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* of the finder patterns and estimated module size.
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*
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* @throws \chillerlan\QRCode\Detector\QRCodeDetectorException
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*/
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private function computeDimension(FinderPattern $nw, FinderPattern $ne, FinderPattern $sw, float $size):int{
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$tltrCentersDimension = (int)round($nw->getDistance($ne) / $size);
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$tlblCentersDimension = (int)round($nw->getDistance($sw) / $size);
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$dimension = (int)((($tltrCentersDimension + $tlblCentersDimension) / 2) + 7);
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switch($dimension % 4){
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case 0:
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$dimension++;
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break;
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// 1? do nothing
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case 2:
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$dimension--;
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break;
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case 3:
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throw new QRCodeDetectorException('estimated dimension: '.$dimension);
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}
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if(($dimension % 4) !== 1){
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throw new QRCodeDetectorException('dimension mod 4 is not 1');
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}
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return $dimension;
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}
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/**
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* Attempts to locate an alignment pattern in a limited region of the image, which is
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* guessed to contain it.
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*
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* @param float $overallEstModuleSize estimated module size so far
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* @param int $estAlignmentX x coordinate of center of area probably containing alignment pattern
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* @param int $estAlignmentY y coordinate of above
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* @param float $allowanceFactor number of pixels in all directions to search from the center
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*
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* @return \chillerlan\QRCode\Detector\AlignmentPattern|null if found, or null otherwise
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*/
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private function findAlignmentInRegion(
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float $overallEstModuleSize,
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int $estAlignmentX,
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int $estAlignmentY,
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float $allowanceFactor
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):?AlignmentPattern{
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// Look for an alignment pattern (3 modules in size) around where it should be
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$dimension = $this->matrix->getSize();
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$allowance = (int)($allowanceFactor * $overallEstModuleSize);
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$alignmentAreaLeftX = max(0, ($estAlignmentX - $allowance));
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$alignmentAreaRightX = min(($dimension - 1), ($estAlignmentX + $allowance));
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if(($alignmentAreaRightX - $alignmentAreaLeftX) < ($overallEstModuleSize * 3)){
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return null;
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}
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$alignmentAreaTopY = max(0, ($estAlignmentY - $allowance));
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$alignmentAreaBottomY = min(($dimension - 1), ($estAlignmentY + $allowance));
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if(($alignmentAreaBottomY - $alignmentAreaTopY) < ($overallEstModuleSize * 3)){
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return null;
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}
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return (new AlignmentPatternFinder($this->matrix, $overallEstModuleSize))->find(
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$alignmentAreaLeftX,
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$alignmentAreaTopY,
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($alignmentAreaRightX - $alignmentAreaLeftX),
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($alignmentAreaBottomY - $alignmentAreaTopY),
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);
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}
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/**
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*
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*/
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private function createTransform(
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FinderPattern $nw,
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FinderPattern $ne,
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FinderPattern $sw,
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int $size,
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?AlignmentPattern $ap = null
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):PerspectiveTransform{
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$dimMinusThree = ($size - 3.5);
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if($ap instanceof AlignmentPattern){
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$bottomRightX = $ap->getX();
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$bottomRightY = $ap->getY();
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$sourceBottomRightX = ($dimMinusThree - 3.0);
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$sourceBottomRightY = $sourceBottomRightX;
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}
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else{
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// Don't have an alignment pattern, just make up the bottom-right point
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$bottomRightX = ($ne->getX() - $nw->getX() + $sw->getX());
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$bottomRightY = ($ne->getY() - $nw->getY() + $sw->getY());
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$sourceBottomRightX = $dimMinusThree;
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$sourceBottomRightY = $dimMinusThree;
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}
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return (new PerspectiveTransform)->quadrilateralToQuadrilateral(
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3.5,
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3.5,
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$dimMinusThree,
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3.5,
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$sourceBottomRightX,
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$sourceBottomRightY,
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3.5,
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$dimMinusThree,
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$nw->getX(),
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$nw->getY(),
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$ne->getX(),
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$ne->getY(),
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$bottomRightX,
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$bottomRightY,
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$sw->getX(),
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$sw->getY()
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);
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}
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}
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