or
“How can I downsize large product images but not enlarge small images?”
simple as:
syntax:
$this->helper('catalog/image') ->init($_product, 'image') ->keepFrame(false) ->constrainOnly(true) ->resize(650);
example:
$this->helper('catalog/image') ->init($_product, 'image') ->keepFrame(false) ->constrainOnly(true) ->resize(650);