PHP图片等比例缩放生成缩略图函数分享

<?php
    /*
    *@im     //需要缩放的图片资源
    *@filetype //制作的缩略图文件类型
    *@dstimw   //缩放的图片的宽度
    *@dstimh  //缩放的图片的高度
    *@thumbname //缩略图文件名字
function makethumb($im,$dstimw,$dstimh,$thumbname ,$filetype){
            //获取im的宽度和高度
        $pic_w=imagesx($im);
        $pic_h=imagesy($im);
        $arr = array();
            swith($filetype){
                case 'jpg':
                        $arr[$filetype]="imagejpeg";
                        break;
                case 'png';
                        $arr[$filetype]="imagepng";
                        break;
                case 'jif';
                        $arr[$filetype]="imagegif";
                }
        if(($dstimgw && $dstimgw<$pic_w) || ($dstimgh && $dstimgh<$pic_h) ){
                if($dstimgw && $dstimgw<$pic_w){
                    $dsimgwratio = $dstimgw / $pic_w;
                    $resizereagw =true;

                }
                if($dstimgh && $ $dstimgh <$pic_h){
                    $dsimghratio = $dstimgh/$pic_h;
                    $resizerreagh =true;
                }
                //缩略图宽高和原图宽高比，取最小的那个
                if($resizereagw && $resizerreagh){
                    if($dsimgwratio<$dsimghratio)
                        $radio = $dsimgwratio;
                    else
                        $radio = $dsimghratio;     
                }
                if($resizereagw && !$resizerreagh ){
                        $radio = $dsimgwratio;
                }
                if(!$resizereagw && $resizerreagh){
                       $radio = $dsimghratio ;
                }
                $imgneww = $pic_w * $radio;
                $imgnewh = $pic_h * $radio;
                if(function_exists("imgcopyresampled")){
                      //创建目标资源画布
                    $dst = imagecreatetruecolor ($imgneww, $imgnewh);
                    imagecopyresampled ($dst,$im,0,0,0,0,$imgneww,$imgnewh,$pic_w,$pic_h);
                }else{
             $dst=imagecreate($imgneww, $imgnewh);
             imagecopyresized ($dst, $im,0,0,0,0,$imgneww,$imgnewh,$imgnewh,$pic_w,$pic_h);
                }

        $arr[$filetype]($dst,$thumbname.".$filetype");
        imagedestroy ($dst);
    }else{//缩略图自身的宽和高已经大于了原图的宽和高
           //则缩略图的宽和缩略的高就是原图的宽和原图的高
         $arr[$filetype]($im,$thumbname.".$filetype");
         imagedestroy();
    }
}
?>