给图片加水印

<?php
/**
  * 功能：给一张图片加上水印效果
  *           $i  要加水印效果的图片
  *           $t  水印文字
  *           $size 文字大小
  *           $pos 水印的位置
  *   		   $color 文字的颜色
  *           $flag 是布尔值，主要用来区分是不是原图上加水印
  *           $type 如果$flag等于false 则新图上加上水印 新文件名为 原名_txt.jpg
  */
function txt($i,$t='版权所有',$size=25,$pos=5,$color='rand',$flag=true,$type='_txt'){
	$img = imagecreatefromjpeg($i);
	$w = imagesx($img);
	$h = imagesy($img);
	$font = dirname(__FILE__).'/font/ls.ttf';
	$ps = imagettfbbox($size,0,$font,$t);
	$tw = $ps[4];
	$th = abs($ps[5]);
	switch($pos){
		case 1:break;	
		case 2:break;	
		case 3:break;	
		case 4:break;	
		case 5:$x=($w-$tw)/2;$y=($h-$th)/2+$th;break;	
		case 6:break;	
		case 7:break;	
		case 8:break;	
		case 9:break;	
		default:break;
	}
	$c = getcolor($img,$color);
	imagettftext($img,$size,0,$x,$y,$c,$font,$t);
	if($flag){
		imagejpeg($img,$i);	
	}else{
		$ext = ext($i);
		$ppp = rtrim($i,'.'.$ext);
		$ppp = $ppp.$type.'.'.$ext;
		imagejpeg($img,$ppp);
	}
}

function getcolor($i,$c='rand',$a=50){
	$cc = '';
	switch($c){
		case 'white':$cc=imagecolorallocatealpha($i,255,255,255,$a);break;
		case 'black':$cc=imagecolorallocatealpha($i,0,0,0,$a);break;
		case 'red':$cc=imagecolorallocatealpha($i,255,0,0,$a);break;
		case 'green':$cc=imagecolorallocatealpha($i,0,255,0,$a);break;
		case 'blue':$cc=imagecolorallocatealpha($i,0,0,255,$a);break;
		case 'orange':$cc=imagecolorallocatealpha($i,0xff,0x66,0x33,$a);break;
		case 'yellow':$cc=imagecolorallocatealpha($i,255,255,0,$a);break;
		case 'rand':$cc=imagecolorallocatealpha($i,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255),$a);break;
		default:
			$cs = substr($c,1);
			$ok = str_split($cs,2);
			$cc = imagecolorallocatealpha($i,hexdec($ok[0]),hexdec($ok[1]),hexdec($ok[2]),$a);
		break;		
	}
	return $cc;
}


/**
 * 功能是：返回扩展名
 */
 
function ext($f){
	$exts = explode('.',$f);
	return end($exts);
}

/**
  *  功能是：返回文件名，不含扩展名
  */
function name($f){
	$s = explode('/',$f);
	$fn = end($s);
	return rtrim($fn,'.'.ext($f));
}