Irregular Polygon Centroid Points in PHP
by Francis[ Edit ] 2012-10-12 12:43:12
Irregular Polygon Centroid Points in PHP
Easy to find the center of irregular polygon points.
<?php
$polygon = array(10,10, 10,50, 75,10, 100,100); // Points for Polygons
print_r(centroid($polygon, 4)); // Print centroid Points
function centroid($polygon,$n) // Find Centroid points using this function
{
$a = area($polygon,$n);
$cx = 0;
$cy = 0;
$polygon=array_chunk($polygon,2);
for ($i=0;$i<$n;$i++)
{
$cx += ($polygon[$i][0] + $polygon[$i+1][0]) * ( ($polygon[$i][0]*$polygon[$i+1][1]) - ($polygon[$i+1][0]*$polygon[$i][1]) );
$cy += ($polygon[$i][1] + $polygon[$i+1][1]) * ( ($polygon[$i][0]*$polygon[$i+1][1]) - ($polygon[$i+1][0]*$polygon[$i][1]) );
}
return(array( (1/(6*$a))*$cx,(1/(6*$a))*$cy));
}
function area($polygon,$n) // Area of Polygon, Its to use find the centroid
{
$polygon=array_chunk($polygon,2);
$area = 0;
for ($i=0;$i<$n;$i++)
{
$j = ($i + 1);
$area += $polygon[$i][0] * $polygon[$j][1];
$area -= $polygon[$i][1] * $polygon[$j][0];
}
$area /= 2;
return(abs($area));
}
?>
