(PECL imagick 2.0.0)
ImagickDraw::polygon — Draws a polygon
$coordinates
   )This function is currently not documented; only its argument list is available.
Draws a polygon using the current stroke, stroke width, and fill color or texture, using the specified array of coordinates.
coordinatesmultidimensional array like array( array( 'x' => 3, 'y' => 4 ), array( 'x' => 2, 'y' => 6 ) );
   Returns TRUE on success.
  
Example #1 ImagickDraw::polygon()
<?php
function polygon($strokeColor, $fillColor, $backgroundColor) {
    $draw = new \ImagickDraw();
    $draw->setStrokeOpacity(1);
    $draw->setStrokeColor($strokeColor);
    $draw->setStrokeWidth(4);
    $draw->setFillColor($fillColor);
    $points = [
        ['x' => 40 * 5, 'y' => 10 * 5],
        ['x' => 20 * 5, 'y' => 20 * 5], 
        ['x' => 70 * 5, 'y' => 50 * 5], 
        ['x' => 60 * 5, 'y' => 15 * 5],
    ];
    $draw->polygon($points);
    $image = new \Imagick();
    $image->newImage(500, 300, $backgroundColor);
    $image->setImageFormat("png");
    $image->drawImage($draw);
    header("Content-Type: image/png");
    echo $image->getImageBlob();
}
?>