利用PHP的GD库相关函数，实现给图片添加水印功能

<?php

$quality = 95;

if(count($argv) < 3) {
    echo "Useage: php {$argv[0]} image_file water_message \n";
    exit();
}

if (file_exists($argv[1]) == false) {
    echo "File Can not Found: {$argv[1]} \n";
    exit();
}

$dst = imagecreatefromstring(file_get_contents($argv[1]));

$color = imagecolorallocate($dst, 255, 0, 0);

for ($i=0; $i < 20; $i++) {
    imagettftext($dst, 50, 45, 100 * $i, 100 * $i, $color, './SourceHanSans-Normal.otf', str_pad($argv[2], 200, $argv[2]));
}

imagejpeg($dst, $argv[1] . '-water.jpg', $quality);

imagedestroy($dst);

用法：

php main.php test.jpg 我是水印