Screenshot of the Labeler. The Labeler provides an image viewer (a) including all navigation functions as with the other tools, but is extended with the ability to place arbitrary numbers of graphical objects/labels on single images/channels. A toolbar (b) allows users to adjust and modify several label properties such as geometry, color or size (c) and provides the option to store sets of labels to the database. Single annotations can be characterized by specific semantic types that can be selected from a predefined list of existing types (d) or by adding new user-defined label types and categories (e). In (f) an annotation chat window is shown, illustrating a current state of conversation of two users about the selected label.