I need to change all uploaded files to 72 dpi. I'm using the php imagick extension.

heres ne denedim (ben kullanıyorum görüntü 300dpi ise):

$image = new Imagick();
$image->setResolution(72,72) ;
$image->readImage($img);
$image->resampleImage  (72,72,imagick::FILTER_UNDEFINED,1);
$image->writeImage($target)

this doesn't seem to anything. the image is uploading, but stays at 300dpi