PHP | imagecreatetruecolor() Function

<?php
  
// Set the vertices of polygon
$values = array(
            150,  50, // Point 1 (x, y)
            50, 250,  // Point 2 (x, y)
            250,  250 // Point 3 (x, y)
        );
    
// Create the size of image or blank image
$image = imagecreatetruecolor(300, 300);
  
// Set the background color of image
$background_color = imagecolorallocate($image,  0, 153, 0);
   
// Fill background with above selected color
imagefill($image, 0, 0, $background_color);
 
// Allocate a color for the polygon
$image_color = imagecolorallocate($image, 255, 255, 255);
   
// Draw the polygon
imagepolygon($image, $values, 3, $image_color);
   
// Output the picture to the browser
header('Content-type: image/png');
   
imagepng($image);
?>

<?php
 
// Create the size of image or blank image.
$image = imagecreatetruecolor(500, 300);
 
// Display the height of image.
echo imagesy($image);
 
?>