From Joomla! Documentation
The media form field type provides modal access to the media manager for the choice of an image. Users with appropriate permissions will be able to upload files.
- type (mandatory) must be media.
- name (mandatory) is the unique name of the field.
- label (mandatory) (translatable) is the descriptive title of the field.
- description (optional) (translatable) is text that will be shown as a tooltip when the user moves the mouse over the drop-down box.
- directory (optional) is the directory from which the user will be able to choose a file. This attribute should be relative to the top level
/images/folder. The default is that the user will be confined to the top level
- preview (optional) shows or hides the preview of the currently chosen image. ("true": Show always, "tooltip": Show as tooltip, "false": Show never). Default is "tooltip". (since Joomla! 2.5.5)
- preview_width (optional) sets the max-width of preview image (default: "200").
- preview_height (optional) sets the max-height of preview image (default: "200").
Example XML field definition:
<field name="myimage" type="media" directory="stories" />
This will open the media manager with the directory
/images/stories/ already selected.
Note that if you are using this field on the frontend then permissions restrictions are likely to be in force. If the user is not authorised to view or add media they will see an error page in the modal popup ("403 You are not authorised to view this resource.").