출처: https://php.365ok.co.kr/image.examples.merged-watermark.php

PHP 이미지 처리 및 GD imagecopymerge를 사용하여 반투명 워터마크 만들기 (365ok.co.kr)

<?php

// Load the stamp and the photo to apply the watermark to

$im = imagecreatefromjpeg('photo.jpeg');

// First we create our stamp image manually from GD

$stamp = imagecreatetruecolor(100, 70);

imagefilledrectangle($stamp, 0, 0, 99, 69, 0x0000FF);

imagefilledrectangle($stamp, 9, 9, 90, 60, 0xFFFFFF);

imagestring($stamp, 5, 20, 20, 'libGD', 0x0000FF);

imagestring($stamp, 3, 20, 40, '(c) 2007-9', 0x0000FF);

// Set the margins for the stamp and get the height/width of the stamp image

$marge_right = 10;

$marge_bottom = 10;

$sx = imagesx($stamp);

$sy = imagesy($stamp);

// Merge the stamp onto our photo with an opacity of 50%

imagecopymerge($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp), 50);

// Save the image to file and free memory

imagepng($im, 'photo_stamp.png');

imagedestroy($im);

?>