$image_path = "123.png";

function watermark_image($oldimage_name, $new_image_name)
/{
global $image_path;
list($owidth,$oheight) = getimagesize($oldimage_name);
$width = $height = 300;
$im = imagecreatetruecolor($width, $height);
$img_src = imagecreatefromjpeg($oldimage_name);
imagecopyresampled($im, $img_src, 0, 0, 0, 0, $width, $height, $owidth, $oheight);
$watermark = imagecreatefrompng($image_path);
list($w_width, $w_height) = getimagesize($image_path);
$pos_x = $width - $w_width;
$pos_y = $height - $w_height;
imagecopy($im, $watermark, $pos_x, $pos_y, 0, 0, $w_width, $w_height);
imagejpeg($im, $new_image_name, 100);
imagedestroy($im);
unlink($oldimage_name);
return true;
}