How can the GD image resource type be properly utilized in PHP classes to ensure compatibility with GD functions like imagepng()?

To ensure compatibility with GD functions like imagepng(), the GD image resource type in PHP classes should be properly handled and passed as a parameter to the GD functions. This can be achieved by creating a method within the class that accepts the GD image resource as an argument and then calls the necessary GD functions on that resource.

class ImageProcessor {
    private $imageResource;

    public function __construct($imagePath) {
        $this->imageResource = imagecreatefromjpeg($imagePath);
    }

    public function saveAsPNG($outputPath) {
        imagepng($this->imageResource, $outputPath);
    }
}

// Example usage
$imageProcessor = new ImageProcessor('input.jpg');
$imageProcessor->saveAsPNG('output.png');