水印带有黑色的描边，并且改变水印颜色不管用。

//打开图片

$src = "p.png";

$info = getimagesize($src);

// echo "<pre>";

// print_r($info);

$type = image_type_to_extension($info[2],false);

$fun = "imagecreatefrom{$type}";

$image = $fun($src);

//操作图片

$font = "msyh.ttf";

$content = "你好慕课";

// $content=iconv("GB2312","UTF-8",$content);

$col = imagecolorallocatealpha($image, 255, 255, 255, 50);

imagettftext($image, 40, 20, 100, 500, $col, $font, $content);

//输出图片

ob_clean();

header("Content-type:".$info['mime']);

$func = "image{$type}";

$func($image);

//保存图片

$func($image,'newimage1.'.$type);

//销毁图片

imagedestroy($image);