Check wether a collection should load an attribute

Observer.php

<?php
class Observer {
    protected function _collectionShouldLoadWidthAndHeight(Mage_Catalog_Model_Resource_Product_Collection $collection)
    {
        $reflection = new ReflectionProperty($collection, '_selectAttributes');
        $reflection->setAccessible(true);
        $value = $reflection->getValue($collection);
        return array_key_exists('original_height', $value) || array_key_exists('original_width', $value);
    }
}