Your post is confusing so my answer could be off.
Something like this should set you on the right path (not tested)
$html = file_get_html($url);
foreach($html->find('img')->parent('a') as $element)
{
$page_url = url_to_absolute($url, $element->href);
$page_html = file_get_html($page_url);
}
But the only true way you can check an image width/height is by copying it to your server first and using getimagesize()
to get height and width.