PHP GD Functions

The number of elements in $points must be equal to twice the number in $num_points.

Contrary to the function imagepolygon, no line is drawn between the last and the first point.

This function is only available for PHP 7.2.0 or higher.

This function returns TRUE on success or FALSE on failure.


<?php

bool imageopenpolygon ( GdImage $image, 
                                              array $points, 
                                                  int $num_points, 
                                                  int $color )

where,

$image = The image identifier

$points = An ARRAY containing the 
                                 coordinates of the polygon vertices

$num_points = The number of vertices of the polygon

$color = The color as returned by imagecolorallocate

?>

$image

The image identifier.

$points

An ARRAY containing the coordinates of the polygon vertices.

$num_points

The number of vertices of the polygon.

$color

The color identifier created by imagecolorallocate.

EXERCISE


<?php

echo 'PHP VERSION: ' . PHP_VERSION . '<br><br>';

$base_img = "png/baseXx.png";

$dest_img = "png/PNG 065 01 imageopenpolygon.png";

$id_polig = imagecreatefrompng($base_img);

$colorln = imagecolorallocate($id_polig, 255, 0, 0);

$star = [191,90, 209,142, 264,143, 220,177, 
                         236,230, 191,199, 146,231, 
                         161,177, 119,143, 172,143]; 
                         
$starv = (count($star)/2);

imageantialias($id_polig, 1);

$polystar = 
imageopenpolygon($id_polig, $star, $starv, $colorln);

$quality = 9;

$filter = 4; 
// PNG_FILTER_PAETH

imagepng($id_polig, $dest_img, $quality, $filter);

echo $dest_img; ?>
<br><br><img src="<?php echo $dest_img; ?>" 
alt="<?php echo $dest_img; ?>">