PHP生成同比例的缩略图实现程序

 
/**********************
*@filename - path to the image
*@tmpname - temporary path to thumbnail
*@xmax - max width
*@ymax - max height
*/
function resize_image($filename, $tmpname, $xmax, $ymax)
{
    $ext = explode(".", $filename);
    $ext = $ext[count($ext)-1];

    if($ext == "jpg" || $ext == "jpeg")
        $im = imagecreatefromjpeg($tmpname);
    elseif($ext == "png")
        $im = imagecreatefrompng($tmpname);
    elseif($ext == "gif")
        $im = imagecreatefromgif($tmpname);

    $x = imagesx($im);
    $y = imagesy($im);

    if($x <= $xmax && $y <= $ymax)
        return $im;

    if($x >= $y) {
        $newx = $xmax;
        $newy = $newx * $y / $x;
    }
    else {
        $newy = $ymax;
        $newx = $x / $y * $newy;
    }

    $im2 = imagecreatetruecolor($newx, $newy);
    imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y);
    return $im2;
}

function creat_thumbnail($img,$w,$h,$path)
{
 $org_info = getimagesize($img); //获得图像大小且是通过post传递过来的
 //var_dump($org_info);
 //Array ( [0] => 1024 [1] => 768 [2] => 3 [3] => width="1024" height="768" [bits] => 8 [mime] => image/png )
 $orig_x = $org_info[0]; //图像宽度
 $orig_y = $org_info[1]; //图像高度
 $orig_type = $org_info[2]; //图片类别即后缀 1 = GIF，2 = JPG，3 = PNG，

 //是真彩色图像
 if (function_exists("imagecreatetruecolor"))
 {
  switch($orig_type)
  {
   //从给定的gif文件名中取得的图像
   case 1  : $thumb_type = ".gif"; $_creatImage = "imagegif"; $_function = "imagecreatefromgif";
   break;
   //从给定的jpeg,jpg文件名中取得的图像
   case 2  : $thumb_type = ".jpg"; $_creatImage = "imagejpeg"; $_function = "imagecreatefromjpeg";
   break;
   //从给定的png文件名中取得的图像
   case 3  : $thumb_type = ".png"; $_creatImage = "imagepng"; $_function = "imagecreatefrompng";
   break;
  }
 }
 //如果从给定的文件名可取得的图像
 if(function_exists($_function))
 {
  $orig_image = $_function($img); //从给定的$img文件名中取得的图像
 }
 if (($orig_x / $orig_y) >= (4 / 3)) //如果宽/高 >= 4/3
 {
  $y = round($orig_y / ($orig_x / $w)); //对浮点数进行四舍五入
  $x = $w;
 }
 else //即 高/宽 >= 4/3
 {
  $x = round($orig_x / ($orig_y / $h));
  $y = $h;
 }
 $sm_image = imagecreatetruecolor($x, $y); //创建真彩色图片
 //重采样拷贝部分图像并调整大小
 Imagecopyresampled($sm_image, $orig_image, 0, 0, 0, 0, $x, $y, $orig_x, $orig_y);
 //imageJPEG($sm_image, '', 80); //在浏览器输出图像
 $tnpath = $path."/"."s_".date('YmdHis').$thumb_type; //缩略图的路径
 $thumbnail = @$_creatImage($sm_image, $tnpath, 80); //生成图片,成功返回true(或1)
 imagedestroy ($sm_image); //销毁图像
 if($thumbnail==true)
 {
  return $tnpath;
 }
}