Pinging an image from a string
<?php
/* read image contents */
$image = file_get_contents("test.jpg");
/* create new imagick object */
$im = new Imagick();
/* pass the string to the imagick object */
$im->pingImageBlob($image);
/* output image width and height */
echo $im->getImageWidth() . 'x' . $im->getImageHeight();
?>