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<?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 <[email protected]> |
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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 RuntimeException; |
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use chillerlan\QRCode\Common\Version; |
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use chillerlan\QRCode\Decoder\BitMatrix; |
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use function abs, is_nan, max, min, round; |
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use function chillerlan\QRCode\Common\distance; |
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use const NAN; |
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/** |
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* <p>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.</p> |
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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 $bitMatrix; |
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/** |
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* Detector constructor. |
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*/ |
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public function __construct(BitMatrix $image){ |
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$this->bitMatrix = $image; |
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} |
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/** |
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* <p>Detects a QR Code in an image.</p> |
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*/ |
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public function detect():BitMatrix{ |
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[$bottomLeft, $topLeft, $topRight] = (new FinderPatternFinder($this->bitMatrix))->find(); |
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$moduleSize = (float)$this->calculateModuleSize($topLeft, $topRight, $bottomLeft); |
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$dimension = $this->computeDimension($topLeft, $topRight, $bottomLeft, $moduleSize); |
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$provisionalVersion = new Version((int)(($dimension - 17) / 4)); |
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$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->bitMatrix, $dimension, $transform); |
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} |
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/** |
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* <p>Computes an average estimated module size based on estimated derived from the positions |
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* of the three finder patterns.</p> |
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* |
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* @throws \RuntimeException |
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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 RuntimeException('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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* <p>Estimates module size based on two finder patterns -- it uses |
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* {@link #sizeOfBlackWhiteBlackRunBothWays(int, int, int, int)} to figure the |
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* width of each, measuring along the axis between their centers.</p> |
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*/ |
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private function calculateModuleSizeOneWay(FinderPattern $pattern, FinderPattern $otherPattern):float{ |
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$moduleSizeEst1 = $this->sizeOfBlackWhiteBlackRunBothWays( |
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$pattern->getX(), |
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$pattern->getY(), |
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$otherPattern->getX(), |
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$otherPattern->getY() |
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); |
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$moduleSizeEst2 = $this->sizeOfBlackWhiteBlackRunBothWays( |
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$otherPattern->getX(), |
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$otherPattern->getY(), |
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$pattern->getX(), |
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$pattern->getY() |
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); |
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if(is_nan($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 + $moduleSizeEst2) / 14.0; |
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} |
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/** |
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* See {@link #sizeOfBlackWhiteBlackRun(int, int, int, int)}; computes the total width of |
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* a finder pattern by looking for a black-white-black run from the center in the direction |
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* of another po$(another finder pattern center), and in the opposite direction too.</p> |
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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 = $this->bitMatrix->getDimension(); |
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// Now count other way -- don't run off image though of course |
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$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)$fromY, (int)$otherToX, (int)$otherToY); |
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// Middle pixel is double-counted this way; subtract 1 |
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return $result - 1.0; |
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} |
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/** |
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* <p>This method traces a line from a po$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.</p> |
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* |
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* <p>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.</p> |
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*/ |
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private function sizeOfBlackWhiteBlackRun(int $fromX, int $fromY, int $toX, int $toY):float{ |
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// Mild variant of Bresenham's algorithm; |
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// see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm |
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$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) === $this->bitMatrix->get($realX, $realY)){ |
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if($state === 2){ |
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return 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($state === 2){ |
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return distance($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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* <p>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.</p> |
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* |
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* @throws \RuntimeException |
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*/ |
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private function computeDimension( |
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FinderPattern $topLeft, |
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FinderPattern $topRight, |
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FinderPattern $bottomLeft, |
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float $moduleSize |
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):int{ |
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$tltrCentersDimension = (int)round($topLeft->distance($topRight) / $moduleSize); |
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$tlblCentersDimension = (int)round($topLeft->distance($bottomLeft) / $moduleSize); |
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$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 RuntimeException('estimated dimension: '.$dimension); |
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} |
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if($dimension % 4 !== 1){ |
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throw new RuntimeException('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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* <p>Attempts to locate an alignment pattern in a limited region of the image, which is |
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* guessed to contain it.</p> |
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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 = $this->bitMatrix->getDimension(); |
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$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->bitMatrix, $overallEstModuleSize))->find( |
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$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 $topLeft, |
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FinderPattern $topRight, |
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FinderPattern $bottomLeft, |
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int $dimension, |
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AlignmentPattern $alignmentPattern = null |
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):PerspectiveTransform{ |
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$dimMinusThree = (float)$dimension - 3.5; |
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if($alignmentPattern instanceof AlignmentPattern){ |
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$bottomRightX = $alignmentPattern->getX(); |
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$bottomRightY = $alignmentPattern->getY(); |
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$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 = ($topRight->getX() - $topLeft->getX()) + $bottomLeft->getX(); |
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$bottomRightY = ($topRight->getY() - $topLeft->getY()) + $bottomLeft->getY(); |
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|
|
$sourceBottomRightX = $dimMinusThree; |
343
|
|
|
$sourceBottomRightY = $dimMinusThree; |
344
|
|
|
} |
345
|
|
|
|
346
|
|
|
return PerspectiveTransform::quadrilateralToQuadrilateral( |
347
|
|
|
3.5, 3.5, |
348
|
|
|
$dimMinusThree, 3.5, |
349
|
|
|
$sourceBottomRightX, $sourceBottomRightY, |
350
|
|
|
3.5, $dimMinusThree, |
351
|
|
|
$topLeft->getX(), $topLeft->getY(), |
352
|
|
|
$topRight->getX(), $topRight->getY(), |
353
|
|
|
$bottomRightX, $bottomRightY, |
354
|
|
|
$bottomLeft->getX(), $bottomLeft->getY() |
355
|
|
|
); |
356
|
|
|
} |
357
|
|
|
|
358
|
|
|
} |
359
|
|
|
|