imagepolygon() function in PHP

The imagepolygon() function is used to draw a polygon on an image resource in PHP. This function is part of the GD library extension and allows you to create polygons with any number of vertices.

Syntax

bool imagepolygon(resource $image, array $points, int $num_points, int $color)

Parameters

• $image − An image resource created with imagecreatetruecolor() or similar functions.
• $points − An array containing the x and y coordinates of the polygon's vertices in sequential order.
• $num_points − The total number of vertices (points) in the polygon.
• $color − A color identifier created with imagecolorallocate() function.

Return Value

The imagepolygon() function returns TRUE on success or FALSE on failure.

Example

The following example demonstrates how to create a triangle using imagepolygon() −

<?php
    $img = imagecreatetruecolor(400, 300);
    $color = imagecolorallocate($img, 120, 160, 190);
    $bgcolor = imagecolorallocate($img, 10, 100, 50);
    
    imagefill($img, 0, 0, $bgcolor);
    
    imagepolygon($img, array(
        50, 50,      // Point 1: x=50, y=50
        150, 200,    // Point 2: x=150, y=200  
        340, 200     // Point 3: x=340, y=200
    ),
    3,
    $color);
    
    header('Content-type: image/png');
    imagepng($img);
    imagedestroy($img);
?>

Output

The above code generates a triangle on a dark green background. The polygon is drawn with light blue color connecting the three specified vertices.

Key Points

• The points array must contain an even number of elements (x,y coordinates).
• The polygon is automatically closed by connecting the last point to the first.
• Requires the GD extension to be enabled in PHP.
• Use imagedestroy() to free memory after image processing.

Conclusion

The imagepolygon() function provides an easy way to draw polygons of any shape on PHP-generated images. It's particularly useful for creating geometric shapes, charts, and custom graphics in web applications.