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<?php |
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/** |
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* Class GridSampler |
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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 Exception, RuntimeException; |
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use chillerlan\QRCode\Decoder\BitMatrix; |
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use function array_fill, count, sprintf; |
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/** |
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* Implementations of this class can, given locations of finder patterns for a QR code in an |
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* image, sample the right points in the image to reconstruct the QR code, accounting for |
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* perspective distortion. It is abstracted since it is relatively expensive and should be allowed |
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* to take advantage of platform-specific optimized implementations, like Sun's Java Advanced |
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* Imaging library, but which may not be available in other environments such as J2ME, and vice |
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* versa. |
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* |
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* The implementation used can be controlled by calling {@link #setGridSampler(GridSampler)} |
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* with an instance of a class which implements this interface. |
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* |
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* @author Sean Owen |
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*/ |
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final class GridSampler{ |
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/** |
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* <p>Checks a set of points that have been transformed to sample points on an image against |
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* the image's dimensions to see if the point are even within the image.</p> |
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* |
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* <p>This method will actually "nudge" the endpoints back onto the image if they are found to be |
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* barely (less than 1 pixel) off the image. This accounts for imperfect detection of finder |
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* patterns in an image where the QR Code runs all the way to the image border.</p> |
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* |
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* <p>For efficiency, the method will check points from either end of the line until one is found |
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* to be within the image. Because the set of points are assumed to be linear, this is valid.</p> |
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* |
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* @param \chillerlan\QRCode\Decoder\BitMatrix $bitMatrix image into which the points should map |
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* @param float[] $points actual points in x1,y1,...,xn,yn form |
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* |
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* @throws \RuntimeException if an endpoint is lies outside the image boundaries |
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*/ |
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private function checkAndNudgePoints(BitMatrix $bitMatrix, array $points):void{ |
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$dimension = $bitMatrix->getDimension(); |
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$nudged = true; |
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$max = count($points); |
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// Check and nudge points from start until we see some that are OK: |
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for($offset = 0; $offset < $max && $nudged; $offset += 2){ |
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$x = (int)$points[$offset]; |
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$y = (int)$points[$offset + 1]; |
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if($x < -1 || $x > $dimension || $y < -1 || $y > $dimension){ |
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throw new RuntimeException(sprintf('checkAndNudgePoints 1, x: %s, y: %s, d: %s', $x, $y, $dimension)); |
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} |
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$nudged = false; |
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if($x === -1){ |
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$points[$offset] = 0.0; |
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$nudged = true; |
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} |
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elseif($x === $dimension){ |
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$points[$offset] = $dimension - 1; |
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$nudged = true; |
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} |
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if($y === -1){ |
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$points[$offset + 1] = 0.0; |
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$nudged = true; |
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} |
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elseif($y === $dimension){ |
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$points[$offset + 1] = $dimension - 1; |
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$nudged = true; |
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} |
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} |
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// Check and nudge points from end: |
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$nudged = true; |
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for($offset = count($points) - 2; $offset >= 0 && $nudged; $offset -= 2){ |
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$x = (int)$points[$offset]; |
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$y = (int)$points[$offset + 1]; |
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if($x < -1 || $x > $dimension || $y < -1 || $y > $dimension){ |
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throw new RuntimeException(sprintf('checkAndNudgePoints 2, x: %s, y: %s, d: %s', $x, $y, $dimension)); |
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} |
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$nudged = false; |
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if($x === -1){ |
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$points[$offset] = 0.0; |
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$nudged = true; |
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} |
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elseif($x === $dimension){ |
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$points[$offset] = $dimension - 1; |
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$nudged = true; |
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} |
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if($y === -1){ |
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$points[$offset + 1] = 0.0; |
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$nudged = true; |
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} |
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elseif($y === $dimension){ |
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$points[$offset + 1] = $dimension - 1; |
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$nudged = true; |
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} |
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} |
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} |
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/** |
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* Samples an image for a rectangular matrix of bits of the given dimension. The sampling |
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* transformation is determined by the coordinates of 4 points, in the original and transformed |
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* image space. |
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* |
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* @return \chillerlan\QRCode\Decoder\BitMatrix representing a grid of points sampled from the image within a region |
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* defined by the "from" parameters |
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* @throws \RuntimeException if image can't be sampled, for example, if the transformation defined |
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* by the given points is invalid or results in sampling outside the image boundaries |
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*/ |
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public function sampleGrid(BitMatrix $image, int $dimension, PerspectiveTransform $transform):BitMatrix{ |
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if($dimension <= 0){ |
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throw new RuntimeException('invalid matrix size'); |
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} |
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$bits = new BitMatrix($dimension); |
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$points = array_fill(0, 2 * $dimension, 0.0); |
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for($y = 0; $y < $dimension; $y++){ |
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$max = count($points); |
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$iValue = (float)$y + 0.5; |
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for($x = 0; $x < $max; $x += 2){ |
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$points[$x] = (float)($x / 2) + 0.5; |
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$points[$x + 1] = $iValue; |
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} |
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$transform->transformPoints($points); |
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// Quick check to see if points transformed to something inside the image; |
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// sufficient to check the endpoints |
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$this->checkAndNudgePoints($image, $points); |
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try{ |
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for($x = 0; $x < $max; $x += 2){ |
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if($image->get((int)$points[$x], (int)$points[$x + 1])){ |
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// Black(-ish) pixel |
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$bits->set($x / 2, $y); |
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} |
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} |
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} |
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catch(Exception $aioobe){//ArrayIndexOutOfBoundsException |
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// This feels wrong, but, sometimes if the finder patterns are misidentified, the resulting |
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// transform gets "twisted" such that it maps a straight line of points to a set of points |
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// whose endpoints are in bounds, but others are not. There is probably some mathematical |
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// way to detect this about the transformation that I don't know yet. |
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// This results in an ugly runtime exception despite our clever checks above -- can't have |
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// that. We could check each point's coordinates but that feels duplicative. We settle for |
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// catching and wrapping ArrayIndexOutOfBoundsException. |
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throw new RuntimeException('ArrayIndexOutOfBoundsException'); |
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} |
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} |
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return $bits; |
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} |
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} |
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chillerlan /
php-qrcode
