The Image constraint works exactly like the :doc:`File</reference/constraints/File>` constraint, except that its mimeTypes and mimeTypesMessage options are automatically setup to work for image files specifically.
See the :doc:`File</reference/constraints/File>` constraint for the bulk of the documentation on this constraint.
This constraint shares all of its options with the :doc:`File</reference/constraints/File>` constraint. It does, however, modify two of the default option values:
type: array or string default: an array of jpg, gif and png image mime types
type: string default: This file is not a valid image