PDF to PNG using php and imagick

I'm trying the best way, via the web, to load a PDF (Large and high quality file) and transform it into an image, which will be displayed in an APP, that is, it has quality but can not be "heavy" so as not to damage the performace of the app at the time of loading. However the user of the application can give zomm to see well what is written and the figures themselves, as a market tabloid, best example I can give.

hj I'm doing this:

$imagick = new Imagick();
$imagick->setResolution(288,288);
$imagick->readImage($arquivo);
$imagick->setImageFormat( "png" );      

foreach($imagick as $i=>$imagick) {

    $imagepng = md5(uniqid(time())).'.png';
    $$imagick->writeImage('../galeria/'.$imagepng.'');

}

Would that be the best way? what can you help me to refine this big, quality and heavy PDF transformation - to great quality IMAGE however well light ????

Thank you.