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<?php
declare(strict_types = 1);
namespace BaconQrCode\Renderer\Module\EdgeIterator;
use BaconQrCode\Encoder\ByteMatrix;
use IteratorAggregate;
use Traversable;
/**
* Edge iterator based on potrace.
*/
final class EdgeIterator implements IteratorAggregate
{
/**
* @var int[]
*/
private $bytes = [];
/**
* @var int
*/
private $size;
/**
* @var int
*/
private $width;
/**
* @var int
*/
private $height;
public function __construct(ByteMatrix $matrix)
{
$this->bytes = iterator_to_array($matrix->getBytes());
$this->size = count($this->bytes);
$this->width = $matrix->getWidth();
$this->height = $matrix->getHeight();
}
/**
* @return Traversable<Edge>
*/
public function getIterator() : Traversable
{
$originalBytes = $this->bytes;
$point = $this->findNext(0, 0);
while (null !== $point) {
$edge = $this->findEdge($point[0], $point[1]);
$this->xorEdge($edge);
yield $edge;
$point = $this->findNext($point[0], $point[1]);
}
$this->bytes = $originalBytes;
}
/**
* @return int[]|null
*/
private function findNext(int $x, int $y) : ?array
{
$i = $this->width * $y + $x;
while ($i < $this->size && 1 !== $this->bytes[$i]) {
++$i;
}
if ($i < $this->size) {
return $this->pointOf($i);
}
return null;
}
private function findEdge(int $x, int $y) : Edge
{
$edge = new Edge($this->isSet($x, $y));
$startX = $x;
$startY = $y;
$dirX = 0;
$dirY = 1;
while (true) {
$edge->addPoint($x, $y);
$x += $dirX;
$y += $dirY;
if ($x === $startX && $y === $startY) {
break;
}
$left = $this->isSet($x + ($dirX + $dirY - 1 ) / 2, $y + ($dirY - $dirX - 1) / 2);
$right = $this->isSet($x + ($dirX - $dirY - 1) / 2, $y + ($dirY + $dirX - 1) / 2);
if ($right && ! $left) {
$tmp = $dirX;
$dirX = -$dirY;
$dirY = $tmp;
} elseif ($right) {
$tmp = $dirX;
$dirX = -$dirY;
$dirY = $tmp;
} elseif (! $left) {
$tmp = $dirX;
$dirX = $dirY;
$dirY = -$tmp;
}
}
return $edge;
}
private function xorEdge(Edge $path) : void
{
$points = $path->getPoints();
$y1 = $points[0][1];
$length = count($points);
$maxX = $path->getMaxX();
for ($i = 1; $i < $length; ++$i) {
$y = $points[$i][1];
if ($y === $y1) {
continue;
}
$x = $points[$i][0];
$minY = min($y1, $y);
for ($j = $x; $j < $maxX; ++$j) {
$this->flip($j, $minY);
}
$y1 = $y;
}
}
private function isSet(int $x, int $y) : bool
{
return (
$x >= 0
&& $x < $this->width
&& $y >= 0
&& $y < $this->height
) && 1 === $this->bytes[$this->width * $y + $x];
}
/**
* @return int[]
*/
private function pointOf(int $i) : array
{
$y = intdiv($i, $this->width);
return [$i - $y * $this->width, $y];
}
private function flip(int $x, int $y) : void
{
$this->bytes[$this->width * $y + $x] = (
$this->isSet($x, $y) ? 0 : 1
);
}
}
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