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2025-10-09 12:14:29 +02:00
commit 684ab3a132
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+<?php
+/**
+ * Class GridSampler
+ *
+ * @created      17.01.2021
+ * @author       ZXing Authors
+ * @author       Smiley <smiley@chillerlan.net>
+ * @copyright    2021 Smiley
+ * @license      Apache-2.0
+ */
+
+namespace chillerlan\QRCode\Detector;
+
+use chillerlan\QRCode\Data\QRMatrix;
+use chillerlan\QRCode\Decoder\BitMatrix;
+use function array_fill, count, intdiv, sprintf;
+
+/**
+ * Implementations of this class can, given locations of finder patterns for a QR code in an
+ * image, sample the right points in the image to reconstruct the QR code, accounting for
+ * perspective distortion. It is abstracted since it is relatively expensive and should be allowed
+ * to take advantage of platform-specific optimized implementations, like Sun's Java Advanced
+ * Imaging library, but which may not be available in other environments such as J2ME, and vice
+ * versa.
+ *
+ * The implementation used can be controlled by calling #setGridSampler(GridSampler)
+ * with an instance of a class which implements this interface.
+ *
+ * @author Sean Owen
+ */
+final class GridSampler{
+
+	private array $points;
+
+	/**
+	 * Checks a set of points that have been transformed to sample points on an image against
+	 * the image's dimensions to see if the point are even within the image.
+	 *
+	 * This method will actually "nudge" the endpoints back onto the image if they are found to be
+	 * barely (less than 1 pixel) off the image. This accounts for imperfect detection of finder
+	 * patterns in an image where the QR Code runs all the way to the image border.
+	 *
+	 * For efficiency, the method will check points from either end of the line until one is found
+	 * to be within the image. Because the set of points are assumed to be linear, this is valid.
+	 *
+	 * @param int $dimension matrix width/height
+	 *
+	 * @throws \chillerlan\QRCode\Detector\QRCodeDetectorException if an endpoint is lies outside the image boundaries
+	 */
+	private function checkAndNudgePoints(int $dimension):void{
+		$nudged = true;
+		$max    = count($this->points);
+
+		// Check and nudge points from start until we see some that are OK:
+		for($offset = 0; $offset < $max && $nudged; $offset += 2){
+			$x = (int)$this->points[$offset];
+			$y = (int)$this->points[($offset + 1)];
+
+			if($x < -1 || $x > $dimension || $y < -1 || $y > $dimension){
+				throw new QRCodeDetectorException(sprintf('checkAndNudgePoints 1, x: %s, y: %s, d: %s', $x, $y, $dimension));
+			}
+
+			$nudged = false;
+
+			if($x === -1){
+				$this->points[$offset] = 0.0;
+				$nudged                = true;
+			}
+			elseif($x === $dimension){
+				$this->points[$offset] = ($dimension - 1);
+				$nudged                = true;
+			}
+
+			if($y === -1){
+				$this->points[($offset + 1)] = 0.0;
+				$nudged                      = true;
+			}
+			elseif($y === $dimension){
+				$this->points[($offset + 1)] = ($dimension - 1);
+				$nudged                      = true;
+			}
+
+		}
+
+		// Check and nudge points from end:
+		$nudged = true;
+
+		for($offset = ($max - 2); $offset >= 0 && $nudged; $offset -= 2){
+			$x = (int)$this->points[$offset];
+			$y = (int)$this->points[($offset + 1)];
+
+			if($x < -1 || $x > $dimension || $y < -1 || $y > $dimension){
+				throw new QRCodeDetectorException(sprintf('checkAndNudgePoints 2, x: %s, y: %s, d: %s', $x, $y, $dimension));
+			}
+
+			$nudged = false;
+
+			if($x === -1){
+				$this->points[$offset] = 0.0;
+				$nudged                = true;
+			}
+			elseif($x === $dimension){
+				$this->points[$offset] = ($dimension - 1);
+				$nudged                = true;
+			}
+
+			if($y === -1){
+				$this->points[($offset + 1)] = 0.0;
+				$nudged                      = true;
+			}
+			elseif($y === $dimension){
+				$this->points[($offset + 1)] = ($dimension - 1);
+				$nudged                      = true;
+			}
+
+		}
+
+	}
+
+	/**
+	 * Samples an image for a rectangular matrix of bits of the given dimension. The sampling
+	 * transformation is determined by the coordinates of 4 points, in the original and transformed
+	 * image space.
+	 *
+	 * @return \chillerlan\QRCode\Decoder\BitMatrix representing a grid of points sampled from the image within a region
+	 *   defined by the "from" parameters
+	 * @throws \chillerlan\QRCode\Detector\QRCodeDetectorException if image can't be sampled, for example, if the transformation defined
+	 *   by the given points is invalid or results in sampling outside the image boundaries
+	 */
+	public function sampleGrid(BitMatrix $matrix, int $dimension, PerspectiveTransform $transform):BitMatrix{
+
+		if($dimension <= 0){
+			throw new QRCodeDetectorException('invalid matrix size');
+		}
+
+		$bits         = new BitMatrix($dimension);
+		$this->points = array_fill(0, (2 * $dimension), 0.0);
+
+		for($y = 0; $y < $dimension; $y++){
+			$max    = count($this->points);
+			$iValue = ($y + 0.5);
+
+			for($x = 0; $x < $max; $x += 2){
+				$this->points[$x]       = (($x / 2) + 0.5);
+				$this->points[($x + 1)] = $iValue;
+			}
+			// phpcs:ignore
+			[$this->points, ] = $transform->transformPoints($this->points);
+			// Quick check to see if points transformed to something inside the image;
+			// sufficient to check the endpoints
+			$this->checkAndNudgePoints($matrix->getSize());
+
+			// no need to try/catch as QRMatrix::set() will silently discard out of bounds values
+#			try{
+				for($x = 0; $x < $max; $x += 2){
+					// Black(-ish) pixel
+					$bits->set(
+						intdiv($x, 2),
+						$y,
+						$matrix->check((int)$this->points[$x], (int)$this->points[($x + 1)]),
+						QRMatrix::M_DATA
+					);
+				}
+#			}
+#			catch(\Throwable $aioobe){//ArrayIndexOutOfBoundsException
+				// This feels wrong, but, sometimes if the finder patterns are misidentified, the resulting
+				// transform gets "twisted" such that it maps a straight line of points to a set of points
+				// whose endpoints are in bounds, but others are not. There is probably some mathematical
+				// way to detect this about the transformation that I don't know yet.
+				// This results in an ugly runtime exception despite our clever checks above -- can't have
+				// that. We could check each point's coordinates but that feels duplicative. We settle for
+				// catching and wrapping ArrayIndexOutOfBoundsException.
+#				throw new QRCodeDetectorException('ArrayIndexOutOfBoundsException');
+#			}
+
+		}
+
+		return $bits;
+	}
+
+}