基于PHP实现等比压缩图片大小

<"start-----------------" ;
if(($maxwidth && $pic_width > $maxwidth) && ($maxheight && $pic_height > $maxheight))
{
if($maxwidth && $pic_width>$maxwidth)
{
$widthratio = $maxwidth/$pic_width;
$resizewidth_tag = true;
}
if($maxheight && $pic_height>$maxheight)
{
$heightratio = $maxheight/$pic_height;
$resizeheight_tag = true;
}
if($resizewidth_tag && $resizeheight_tag)
{
if($widthratio<$heightratio)
$ratio = $widthratio;
else
$ratio = $heightratio;
}
if($resizewidth_tag && !$resizeheight_tag)
$ratio = $widthratio;
if($resizeheight_tag && !$resizewidth_tag)
$ratio = $heightratio;
$newwidth = $pic_width * $ratio;
$newheight = $pic_height * $ratio;
if(function_exists("imagecopyresampled"))
{
$newim = imagecreatetruecolor($newwidth,$newheight);
imagecopyresampled($newim,$im,,,,,$newwidth,$newheight,$pic_width,$pic_height);
}
else
{
$newim = imagecreate($newwidth,$newheight);
imagecopyresized($newim,$im,,,,,$newwidth,$newheight,$pic_width,$pic_height);
}
$name = $name.$filetype;
imagejpeg($newim,$name);
imagedestroy($newim);
}
else
{
$name = $name.$filetype;
imagejpeg($im,$name);
} 
}