A somewhat generic detector that looks for a barcode-like rectangular region within an image. * It looks within a mostly white region of an image for a region of black and white, but mostly * black. It returns the four corners of the region, as best it can determine.

* * @author Sean Owen * @port Ashot Khanamiryan */ class MonochromeRectangleDetector { private static int $MAX_MODULES = 32; public function __construct(private readonly BinaryBitmap $image) { } /** *

Detects a rectangular region of black and white -- mostly black -- with a region of mostly * white, in an image.

* * @return {@link ResultPoint}[] describing the corners of the rectangular region. The first and * last points are opposed on the diagonal, as are the second and third. The first point will be * the topmost point and the last, the bottommost. The second point will be leftmost and the * third, the rightmost * @throws NotFoundException if no Data Matrix Code can be found */ public function detect(): \Zxing\ResultPoint { $height = $this->image->getHeight(); $width = $this->image->getWidth(); $halfHeight = $height / 2; $halfWidth = $width / 2; $deltaY = max(1, $height / (self::$MAX_MODULES * 8)); $deltaX = max(1, $width / (self::$MAX_MODULES * 8)); $top = 0; $bottom = $height; $left = 0; $right = $width; $pointA = $this->findCornerFromCenter( $halfWidth, 0, $left, $right, $halfHeight, -$deltaY, $top, $bottom, $halfWidth / 2 ); $top = (int)$pointA->getY() - 1; $pointB = $this->findCornerFromCenter( $halfWidth, -$deltaX, $left, $right, $halfHeight, 0, $top, $bottom, $halfHeight / 2 ); $left = (int)$pointB->getX() - 1; $pointC = $this->findCornerFromCenter( $halfWidth, $deltaX, $left, $right, $halfHeight, 0, $top, $bottom, $halfHeight / 2 ); $right = (int)$pointC->getX() + 1; $pointD = $this->findCornerFromCenter( $halfWidth, 0, $left, $right, $halfHeight, $deltaY, $top, $bottom, $halfWidth / 2 ); $bottom = (int)$pointD->getY() + 1; // Go try to find po$A again with better information -- might have been off at first. $pointA = $this->findCornerFromCenter( $halfWidth, 0, $left, $right, $halfHeight, -$deltaY, $top, $bottom, $halfWidth / 4 ); return new ResultPoint($pointA, $pointB, $pointC, $pointD); } /** * Attempts to locate a corner of the barcode by scanning up, down, left or right from a center * point which should be within the barcode. * * @param float $centerX center's x component (horizontal) * @param float $deltaX same as deltaY but change in x per step instead * @param int $left * @param int $right * @param float $centerY center's y component (vertical) * @param float $deltaY change in y per step. If scanning up this is negative; down, positive; * left or right, 0 * @param int $top * @param int $bottom * @param float $maxWhiteRun maximum run of white pixels that can still be considered to be within * the barcode * * @return ResultPoint {@link com.google.zxing.ResultPoint} encapsulating the corner that was found * * @throws NotFoundException if such a point cannot be found */ private function findCornerFromCenter( int|float $centerX, int|float $deltaX, int $left, int $right, int|float $centerY, float|int $deltaY, int $top, int $bottom, int|float $maxWhiteRun ): \Zxing\ResultPoint { $lastRange = null; for ($y = $centerY, $x = $centerX; $y < $bottom && $y >= $top && $x < $right && $x >= $left; $y += $deltaY, $x += $deltaX) { $range = 0; if ($deltaX == 0) { // horizontal slices, up and down $range = $this->blackWhiteRange($y, $maxWhiteRun, $left, $right, true); } else { // vertical slices, left and right $range = $this->blackWhiteRange($x, $maxWhiteRun, $top, $bottom, false); } if ($range == null) { if ($lastRange == null) { throw new NotFoundException("No corner from center found"); } // lastRange was found if ($deltaX == 0) { $lastY = $y - $deltaY; if ($lastRange[0] < $centerX) { if ($lastRange[1] > $centerX) { // straddle, choose one or the other based on direction return new ResultPoint($deltaY > 0 ? $lastRange[0] : $lastRange[1], $lastY); } return new ResultPoint($lastRange[0], $lastY); } else { return new ResultPoint($lastRange[1], $lastY); } } else { $lastX = $x - $deltaX; if ($lastRange[0] < $centerY) { if ($lastRange[1] > $centerY) { return new ResultPoint($lastX, $deltaX < 0 ? $lastRange[0] : $lastRange[1]); } return new ResultPoint($lastX, $lastRange[0]); } else { return new ResultPoint($lastX, $lastRange[1]); } } } $lastRange = $range; } throw new NotFoundException("No corner from center found"); } /** * Computes the start and end of a region of pixels, either horizontally or vertically, that could * be part of a Data Matrix barcode. * * @param float|int $fixedDimension * @param float|int $maxWhiteRun * @param int $minDim * @param int $maxDim * @param bool $horizontal * * @return (float|int)[]|null with start and end of found range, or null if no such range is found (e.g. only white was found) * * @psalm-return array{0: float|int, 1: float|int}|null */ private function blackWhiteRange(float|int $fixedDimension, int|float $maxWhiteRun, int $minDim, int $maxDim, bool $horizontal): array|null { $center = ($minDim + $maxDim) / 2; // Scan left/up first $start = $center; while ($start >= $minDim) { if ($horizontal ? $this->image->get($start, $fixedDimension) : $this->image->get($fixedDimension, $start)) { $start--; } else { $whiteRunStart = $start; do { $start--; } while ($start >= $minDim && !($horizontal ? $this->image->get($start, $fixedDimension) : $this->image->get($fixedDimension, $start))); $whiteRunSize = $whiteRunStart - $start; if ($start < $minDim || $whiteRunSize > $maxWhiteRun) { $start = $whiteRunStart; break; } } } $start++; // Then try right/down $end = $center; while ($end < $maxDim) { if ($horizontal ? $this->image->get($end, $fixedDimension) : $this->image->get($fixedDimension, $end)) { $end++; } else { $whiteRunStart = $end; do { $end++; } while ($end < $maxDim && !($horizontal ? $this->image->get($end, $fixedDimension) : $this->image->get($fixedDimension, $end))); $whiteRunSize = $end - $whiteRunStart; if ($end >= $maxDim || $whiteRunSize > $maxWhiteRun) { $end = $whiteRunStart; break; } } } $end--; return $end > $start ? [$start, $end] : null; } }