How it works

The mechanism, under the hood, of the VIMAGE is pretty simple.

In a glance it does the following:

• converts each rule dict (i.e {'SIZE': 100} etc) to a corresponding class.
• each class defines a method which returns a function (callable, the validator)
• a registry is build which has the ImageField as keys and a list of functions (validators) as the value
• finally, each validator is added to the ImageField’s validators attribute (a method defined as a cached_property)

For more info about Model validators refer to validators.