php簡單實用生成縮略圖代碼

本程式是根據使用者上傳圖片後再把上傳的圖片按比例生成縮略圖

<?


$w?$resizewidth=$w:$resizewidth=400;// 生成圖片的寬度


$h?$resizeheight=$h:$resizeheight=400;// 生成圖片的高度


function resizeimage($im,$maxwidth,$maxheight,$name){


    $width = imagesx($im);


    $height = imagesy($im);


    if(($maxwidth && $width > $maxwidth) || ($maxheight && $height > $maxheight)) {


        if($maxwidth && $width > $maxwidth){


            $widthratio = $maxwidth/$width;


            $resizewidth=true;


        }


        if($maxheight && $height > $maxheight){


            $heightratio = $maxheight/$height;


            $resizeheight=true;


        }


        if($resizewidth && $resizeheight){


            if($widthratio < $heightratio){


                $ratio = $widthratio;


            }else{


                $ratio = $heightratio;


            }


}elseif($resizewidth){


            $ratio = $widthratio;


        }elseif($resizeheight){


            $ratio = $heightratio;


        }


        $newwidth = $width * $ratio;


        $newheight = $height * $ratio;


        if(function_exists("imagecopyresampled")){


              $newim = imagecreatetruecolor($newwidth, $newheight);


imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);


        }else{


            $newim = imagecreate($newwidth, $newheight);


              imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);


        }


        imagejpeg ($newim,$name);


        imagedestroy ($newim);


    }else{


        imagejpeg ($im,$name);


    }


}

if($_files['uploadfile']['size']){
    if($_files['uploadfile']['type'] == "image/pjpeg"){
        $im = imagecreatefromjpeg($_files['uploadfile']['tmp_name']);
    }elseif($_files['uploadfile']['type'] == "image/x-png"){
         $im = imagecreatefrompng($_files['uploadfile']['tmp_name']);
    }elseif($_files['uploadfile']['type'] == "image/gif"){
         $im = imagecreatefromgif($_files['uploadfile']['tmp_name']);
    }
    if($im){
        if(file_exists('bbs.jpg')){
            unlink('bbs.jpg');
        }
        resizeimage($im,$resizewidth,$resizeheight,'bbs.jpg');
        imagedestroy ($im);
 
    }
}
//$uploadfile="www.jzread.com.jpg";
?>