require_once("vendor/autoload.php");

use Jcupitt\Vips\Exception;
use Jcupitt\Vips\Image as VipsImage;
use Jcupitt\Vips\BlendMode;

$overlay_file = 'avatar.png';

$overlay = VipsImage::newFromFile($overlay_file);

$file = 'problem-image.jpg';

$image = VipsImage::newFromFile($file);

$x = 50;
$y = 50;

if (!$overlay->hasAlpha()) {
    $overlay = $overlay->bandjoin(255);
}

$watermark_alpha = $overlay[$overlay->bands - 1];
$overlay = $overlay->extract_band(0, ['n' => $watermark->bands - 1]);
$watermark_alpha = $watermark_alpha->multiply((50 / 100));
$overlay = $overlay->bandjoin($watermark_alpha);

$image = $image->composite($overlay, [BlendMode::OVER], ['x' => $x, 'y' => $y]);

$output = 'output.jpg';

$image->writeToFile($output, ['Q' => 70, 'strip' => true, 'optimize_coding' => true, 'background' => 255]);