functiion for cropping an image

function cropImage($picture,$fixedwidth,$fixedheight,$mogrify) {

// GET IMG
$img = imagecreatefromjpeg($picture);
$width= imagesx($img);
$height= imagesy($img);
// CROP WIDTH
if($width!=$fixedwidth){
$ratio =$fixedwidth/$width;
$NewHeight=round($height*$ratio);
$NewWidth=round($width*$ratio);
exec( $mogrify." -resize ".$NewWidth."x".$NewHeight."! $picture");
exec( $mogrify." -crop ".$fixedwidth."x".$fixedheight."+0+0 $picture");
// REFRESH
$img = imagecreatefromjpeg($picture);
$width= imagesx($img);
$height= imagesy($img);
}
// CROP HEIGHT
if($height!=$fixedheight){
$ratio =$fixedheight/$height;
$NewHeight=round($height*$ratio);
$NewWidth=round($width*$ratio);
exec( $mogrify." -resize ".$NewWidth."x".$NewHeight."! $picture");
exec( $mogrify." -crop ".$fixedwidth."x".$fixedheight."+0+0 $picture");
}
//
ImageDestroy($img);
}