UserInteractionVisualTool is the base class for visual tools, which perform interaction between the user and interactive object in ImageViewer using input devices (like keyboard, mouse, etc). The class allows to implement custom (user-defined) logic of interaction between a collection of interactive objects and the user. The classes, which are derived from this class, are visual tools, like AnnotationVisualTool, RectangularSelectionTool, CustomSelectionTool.

Basics concepts of the interactive communication model are:

• Interaction - changing of some object properties (size, location,...) using input devices (like keyboard, mouse etc).
• Interactive object - an object that implements IInteractiveObject interface with which is possible to communicate interactively.
  IInteractiveObject interface defines the base properties of interactive object, necessary for organizing the interaction process:
  
  • IInteractiveObject.InteractionController property defines an interaction controller used for current interactive object
  • IInteractiveObject.GetBoundingBox and IInteractiveObject.GetDrawingBox properties define, appropriately, the object's bounding rectangle and rectangle in which the current object should be drawn
  • IInteractiveObject.IsPointOnObject method determines if the specified point is above the current interactive object
  • IInteractiveObject.GetPointTransform method returns the conversion of points from interactive object coordinate system to the image viewer coordinate system
  • IInteractiveObject.Draw method performs drawing of object on specified System.Drawing.Graphics object
  • IInteractiveObject.StateChanged event indicates the change of interactive object state.
• Interaction controller - an object that defines the logic of communication between some sets of interaction areas and interactive object (e.g. controller of type RectangularObjectTransformer contains a logic of rectangular objects transformation as well as a set of interaction areas with help of which the current object is being transformed).
  Interactive communication controllers implement IInteractionController interface and that provides them with the following properties:
  
  • IInteractionController.InteractionAreas property defines the collection of interaction areas for current controller
  • IInteractionController.OnInteraction method defines the logic of communication between the interaction area and the interactive object
  • IInteractionController.UpdateInteractionAreas method performs updating of interaction areas (their location, visibility, state, etc).
• Interaction area - some area on an object using which the user communicates with interactive object (e.g. the point pulling which the object can be stretched or rotated). The interaction area can be either invisible (e.g. the area using which is performed relocation of object) or visible (e.g. rotation point, rotation assistant).
  Every interaction area is derived from InteractionArea class and has the following features:
  
  • InteractionArea.GetBoundingBox method returns the bounding rectangle of interaction area
  • InteractionArea.IsPointOnArea method determines if the specified point is above the interaction area
  • InteractionArea.Draw method performs drawing of visual representation of the area
  • InteractionArea.InteractionType property defines the type of interactive communication (relocation, click, etc) which affects the logic of OnInteraction event initiation in the interactive communication controller
  • InteractionArea.Cursor property defines the look of cursor when the mouse pointer is over the area
  • InteractionArea.ActionMouseButton property defines the mouse button the current area responds to
• Interaction visual tool - a class, which is derived from UserInteractionVisualTool class and provides the following functionality:
  
  • storing of interactive objects collection
  • displaying of interactive objects in the image viewer
  • choosing of active object (interactive is currently in progress with)
  • displaying of interaction areas of active interaction controller
  • determining of active area and converting of events from input devices (like mouse etc) to the interaction events for transferring to the interaction controller of active object.

Basic working principles of interaction model

The interaction model work can be divided into 5 steps:

1. The interaction visual tool gets the selected object and counted it as active object, the interaction visual tool gets the interaction controller from active object and counted it as active interaction controller.
2. The interaction visual tool performs call of UpdateInteractionAreas method for active interaction controller and gets a list of interaction areas using InteractionAreas property of interaction controller. The interaction visual tool displays interaction areas over other interactive objects in image viewer.
3. The interaction visual tool analyzes events coming from input devices (e.g. mouse button clicking, mouse pointer relocation) and determines the interaction area the user is working with. Events from input devices are converted to the interaction events according to the type of interaction area and then are directed to the active interaction controller using IInteractionController.OnInteraction(InteractionEventArgs) method.
4. The interaction controller in OnInteraction method performs the logic of interaction between interaction area and interactive object. For example: Interactive object supports rotation by implementing the interface of interactive object in which exist RotationAngle property. After the controller receives the interaction event with rotation point (rotation point - interaction area) it will calculate rotation angle on which is necessary to rotate the object and will change object's RotationAngle property for necessary angle.
5. When the interaction controller changes any property, which varies object's state (e.g. Rotation angle), the object will generate StateChanged event to which is subscribed the interaction visual tool. The interaction visual tool will be performing the update of interactive areas in active interaction controller and then redrawing of interactive object and interactive areas in image viewer.

Hierarchy of interactive objects interfaces

IInteractiveObject - the base interface, which defines general characteristics of all interactive objects.

IRectangularInteractiveObject - defines the rectangular object, which supports rotation.

IPointBasedInteractiveObject - defines the object, which consists from set of points.

Note: the fact that properties of interactive objects are described by hierarchy of interfaces, made possible to create interactive objects, which could implement at once several interactive objects interfaces. For example, an object may support overpatching of its base points (IPointBasedInteractiveObject) as well as overpatching of its shape (stretching, compaction, rotation) using rectangular object interface (IRectangularInteractiveObject).

Hierarchy of interaction controllers

The interaction controllers are divided into 2 groups for convenience:

• builders - perform initial building of new object
• transformers - perform transformation of existing object

IInteractionController - the base interface, which defines general characteristics of all interactive communication controllers.

RectangularObjectBuilder - builder of objects implementing IRectangularInteractiveObject interface.

RectangularObjectTransformer - transformer of objects implementing IRectangularInteractiveObject interface. Provides the ability to relocate, stretch, compress, rotate object.

PointBasedObjectPointBuilder - builder of objects implementing IPointBasedInteractiveObject interface. Provides the ability to construct an object by adding to it new points by mouse click.

PointBasedObjectFreehandBuilder - builder of objects implementing IPointBasedInteractiveObject interface. Provides the ability to construct an object by adding to it new points by mouse movement.

PointBasedObjectLineBuilder - builder of objects implementing IPointBasedInteractiveObject interface. Provides the ability to construct an object which consists from two points (line).

PointBasedObjectRectangularBuilder - builder of objects implementing IPointBasedInteractiveObject interface. Provides the ability to construct an object by scaling all its points.

PointBasedObjectPointTransformer - transformer of objects implementing IPointBasedInteractiveObject interface. Provides the ability to mark, relocate, remove, add object's points.

PointBasedObjectRectangularTransformer - transformer of objects implementing IPointBasedInteractiveObject interface. Provides the ability to relocate, stretch, compress, rotate object.

PointBasedObjectDistortionTransformer - transformer of objects implementing [IPointBasedInteractiveObject interface. Provides the ability to apply distortion and skew.

CompositeInteractionController - the composite interaction controller, which can combine the work of multiple interaction controllers and is used to:

• integrate the functionality of multiple interaction controllers, which are working with one interactive object
• merge several controllers, which are working with different interactive objects and thus organize interaction with composite interactive object.

Hierarchy of interaction areas

The base class for all interaction areas is InteractionArea class.

Interaction areas are divided into 3 groups for convenience:

• Points of interactive object:
  
  • InteractionPoint - the interaction point in the shape of circle, characterized by the position and the radius. This area is used as a point of changing the object size in most interaction controllers.
  • InteractionRectangularPoint - the interaction point in the shape of rectangle, characterized by the position and the radius.
  • InteractionPolygonPoint - the interaction point in the shape of rectangle (derived from InteractionRectangularPoint), characterized by the index of object's point with which it is tied. This area is used in controllers of IPointBasedInteractiveObject objects for interaction with the object's points.
  • RotationPoint - the interaction area, which is derived from InteractionPoint and is used to perform object rotation.
  • RotationAssistantArea - the interaction area that defines "rotation assistant" - area in the shape of circle divided into sectors, using which can be performed the rotation of object on exact angle.
• Interaction areas connected with interactive object:
  
  • InteractiveObjectArea - the interaction area that coincides with area of interactive object, which is defined by IInteractiveObject.IsPointOnObject(X,Y) method. This area is used in some interaction controllers for the assignment of area using which is implemented changing of object position.
  • InteractiveObjectBoundingBoxArea - the interaction area that coincides with bounding rectangle of interactive object. This area is used in some interaction controllers for the assignment of area using which is implemented changing of object position.
  • InteractiveObjectBoundingBoxSelection - the interaction area, which is derived from InteractiveObjectBoundingBoxArea. This area is used in some interaction controllers for the designation of object's bounding rectangle area.
• Interaction areas connected with image viewer:
  
  • ImageViewerArea - the area covering the whole image viewer. This area is used in builders for the assignment of object's building area.