/** Computes a set of initial candidates that cover the given region. */
private function getInitialCandidates()
{
// Optimization: if at least 4 cells are desired (the normal case),
// start with a 4-cell covering of the region's bounding cap. This
// lets us skip quite a few levels of refinement when the region to
// be covered is relatively small.
if ($this->maxCells >= 4) {
// Find the maximum level such that the bounding cap contains at most one
// cell vertex at that level.
$cap = $this->region->getCapBound();
$level = min(S2Projections::MIN_WIDTH()->getMaxLevel(2 * $cap->angle()->radians()), min($this->maxLevel(), S2CellId::MAX_LEVEL - 1));
if ($this->levelMod() > 1 && $level > $this->minLevel()) {
$level -= ($level - $this->minLevel()) % $this->levelMod();
}
// We don't bother trying to optimize the level == 0 case, since more than
// four face cells may be required.
if ($level > 0) {
// Find the leaf cell containing the cap axis, and determine which
// subcell of the parent cell contains it.
/** @var S2CellId[] $base */
$base = array();
$s2point_tmp = $cap->axis();
$id = S2CellId::fromPoint($s2point_tmp);
$id->getVertexNeighbors($level, $base);
for ($i = 0; $i < count($base); ++$i) {
// printf("(face=%s pos=%s level=%s)\n", $base[$i]->face(), dechex($base[$i]->pos()), $base[$i]->level());
// echo "new S2Cell(base[i])\n";
$cell = new S2Cell($base[$i]);
// echo "neighbour cell: " . $cell . "\n";
$c = $this->newCandidate($cell);
// if ($c !== null)
// echo "addCandidato getInitialCandidates: " . $c->cell->id() . "\n";
$this->addCandidate($c);
}
// echo "\n\n\n";
return;
}
}
// Default: start with all six cube faces.
$face_cells = self::FACE_CELLS();
for ($face = 0; $face < 6; ++$face) {
$c = $this->newCandidate($face_cells[$face]);
echo "addCandidato getInitialCandidates_default: " . $c->cell->id() . "\n";
$this->addCandidate($c);
}
}
/**
* @param $latitude
* @param $longitude
* @param $width
* @return array
*/
public function getCellIds($latitude, $longitude, $width)
{
$latLng = S2LatLng::fromDegrees($latitude, $longitude);
$cellId = S2CellId::fromLatLng($latLng)->parent(15);
$index = 0;
$jindex = 0;
$level = $cellId->level();
$size = 1 << S2CellId::MAX_LEVEL - $level;
$face = $cellId->toFaceIJOrientation($index, $jindex);
$cells = [];
$halfWidth = floor($width / 2);
for ($x = -$halfWidth; $x <= $halfWidth; $x++) {
for ($y = -$halfWidth; $y <= $halfWidth; $y++) {
$cells[] = S2CellId::fromFaceIJ($face, $index + $x * $size, $jindex + $y * $size)->parent(15)->id();
}
}
return $cells;
}