织梦生成漂亮整齐的缩略图如何实现

if($toWH<=$srcWH){ 
$ftoW=$toW; 
$ftoH=$ftoW*($srcH/$srcW);  
} 
else{ 
$ftoH=$toH; 
$ftoW=$ftoH*($srcW/$srcH);  
}

$ftoH=$toH; 
$ftoW=$toW; 
if ($toWH<=$srcWH) { 
$src_Y = 0; 
$src_X = ($srcW-$srcH*$toWH)/2;  
$srcW = $srcH*$toWH; 
} else { 
$src_X = 0; 
$src_Y = ($srcH-$srcW/$toWH)/2;  
$srcH = $srcW/$toWH; 
}

($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH)

($ni,$im,0,0,$src_X,$src_Y,$ftoW,$ftoH,$srcW,$srcH)