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;
}