relevance-enhanced image reduction

Sometimes I've been looking for a module which would let me crop an image visually, though I haven't found one working for the drupal version I've been using, until recently when Imagefield crop became available (Edit: which supposedly will be folded into Imagecrop for D6. The latter module is a later addition which I weren't aware of when I wrote this.)

However, there is still one missing concept and that is Relevance-Enhanced Image Reduction which is what would be the best solution for this.