For format see:
http://www.imagemagick.org/script/formats.php
(PECL imagick 2, PECL imagick 3)
Imagick::setFormat — Sets the format of the Imagick object
format
Restituisce true
in caso di successo.
You can only set format listed in $imgic->queryFormats() .
It can be different from http://www.imagemagick.org/script/formats.php .