Annotation view in WinForms

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The AnnotationView class is always created on the base of AnnotationData class and defines the annotation's visual appearance and the way the user may interact with annotation.

Link between classes derived from AnnotationData and AnnotationView is registered using the AnnotationViewFactory.RegisterViewForAnnotationData method.

As in the case with classes derived from AnnotationData class, the classes derived from AnnotationView class are divided into 3 types:

views for annotations, which are based on rectangle (base class is RectangleAnnotationView):
- RectangleAnnotationView - defines view for RectangleAnnotationData annotation. This class is the base class for all views of annotations based on rectangle.
- EllipseAnnotationView - defines view for EllipseAnnotationData annotation.
- ImageAnnotationView - defines view for EmbeddedImageAnnotationData annotation.
- ReferencedImageAnnotationView - defines view for ReferencedImageAnnotationData annotation.
- HighlightAnnotationView - defines view for HighlightAnnotationData annotation.
- TextAnnotationView - defines view for TextAnnotationData annotation.
- LinkAnnotationView - defines view for LinkAnnotationData annotation.
- StampAnnotationView - defines view for StampAnnotationData annotation.
views for annotations, which are based on a set of points (base class is LineAnnotationViewBase):
- LineAnnotationView - defines view for LineAnnotationData annotation.
- LinesAnnotationView - defines view for LinesAnnotationData annotation.
- PolygonAnnotationView - defines view for PolygonAnnotationData annotation.
- RulerAnnotationView - defines view for RulerAnnotationData annotation.
- RulersAnnotationView - defines view for RulersAnnotationData annotation.
- AngleAnnotationView - defines view for AngleAnnotationData annotation.
- LeaderLineAnnotationView - defines view for LeaderLineAnnotationData annotation.
views for composite annotations (base class is CompositeAnnotationView):
- FreeTextAnnotationView - defines view for FreeTextAnnotationData annotation. This view is the combination of TextAnnotationView and LeaderLineAnnotationView.
- GroupAnnotationView - defines view for GroupAnnotationData annotation.

AnnotationView class contains the AnnotationView.Data property, which allows to get reference to a linked instance AnnotationData class. Also AnnotationView class contains a set of properties similar to the properties of AnnotationData class, which allow to relay annotation's properties through AnnotationView.

Here is C#/VB.NET code that shows how to create an instance of view for EllipseAnnotationData annotation:

public static Vintasoft.Imaging.Annotation.UI.AnnotationView CreateViewForEllipseAnnotationData(
    Vintasoft.Imaging.Annotation.EllipseAnnotationData ellipseAnnotation)
{
    return new Vintasoft.Imaging.Annotation.UI.EllipseAnnotationView(ellipseAnnotation);
}

VB.NET

Public Shared Function CreateViewForEllipseAnnotationData(ellipseAnnotation As Vintasoft.Imaging.Annotation.EllipseAnnotationData) As Vintasoft.Imaging.Annotation.UI.AnnotationView
    Return New Vintasoft.Imaging.Annotation.UI.EllipseAnnotationView(ellipseAnnotation)
End Function

Annotation bounding rectangles

The visual appearance of annotation has several bounding rectangle types. The following types are used for solving various tasks related to correct drawing and interaction with annotation:

Bounding Box - defines the rectangle aligned by axises, which encloses annotation. That rectangle is defined only by AnnotationView.Location, AnnotationView.Size and AnnotationView.Rotation properties of annotation, and may be used as a basis for Drawing Box calculating. For getting the rectangle is necessary to call AnnotationView.GetBoundingBox method.
Author Bounding Box - defines the rectangle aligned by axises, which by-turn defines the annotation area during annotation transformation, as well as is used for annotation selection in annotation viewer. In most cases Author Bounding Box conforms to Bounding Box area of annotation. For getting the rectangle is necessary to call AnnotationView.GetAuthorBoundingBox method. This method is a virtual one, that's why it's possible to override it in classes derived from AnnotationView class.
Drawing Box - defines the rectangle aligned by axises, which fully encloses the entire visual part of annotation, but nothing more. Drawing Box can be larger than Bounding Box, because of additional visual elements of annotation, like annotation shadow, caption with value of annotation length, smoothinh of interpolated lines, etc.

Focus annotation in WinForms annotation viewer

Every annotation may receive focus in the image viewer. When an annotation is focused there appears a selection rectangle around it, which can be transformed (scaled, mirrored, rotated) and the annotation will be transformed in proportion to the selection rectangle.

The views for annotations, which are based on a set of points, in addition, may be transformed using points. When annotation is selected - all of its points become selected, the user may change the location of each point using dragging.

Also the views for annotations, which are based on a set of points, support composite selection mode, which allows to transform annotation both using selection rectangle and using points.

The selection/transformation mode of annotation, which are based on a set of points, may be changed using LineAnnotationViewBase.GripMode property.

Build and transform annotation in WinForms annotation viewer

AnnotationView.Builder property defines the interactive controller, which is used for annotation building.
AnnotationView.Transformer property defines the interactive controller, which is used for annotation transformation.

Also AnnotationView class has AnnotationView.InteractionController property which defines the currently used interactive controller.
Detailed information about building and transformation of annotation can be found in article: Building and transformation of annotations in WinForms.

Monitor the annotation state

AnnotationView class provides events, which allow to monitor the annotation state:

AnnotationView.Drawing - occurs when the annotation is drawing.
AnnotationView.Drawn - occurs when the annotation is drawn.
AnnotationView.MouseDown - occurs when the mouse pointer is over the annotation and the mouse button is pressed.
AnnotationView.MouseUp - occurs when the mouse pointer is over the annotation and the mouse button is released.
AnnotationView.MouseEnter - occurs when the mouse pointer enters the annotation.
AnnotationView.MouseMove - occurs when the mouse pointer rests on the annotation.
AnnotationView.MouseLeave - occurs when the mouse pointer leaves the annotation.
AnnotationView.MouseWheel - occurs when the mouse wheel moves while the annotation has focus.
AnnotationView.Click - occurs when the annotation is clicked.
AnnotationView.DoubleClick - occurs when the annotation is double-clicked.
AnnotationView.StateChanged - occurs when the state of annotation is changed, e.g. arrived PropertyChanged event from Data object.

Annotation collection

The AnnotationViewCollection class is always created on the base of AnnotationDataCollection class and represents a collection of annotation's views, which are linked with annotation data from AnnotationDataCollection.
The AnnotationViewCollection class makes changes synchronously in its collection and in linked AnnotationDataCollection.
The AnnotationViewCollection class provides the ability to add, remove, reorder, resort elements, transform to AnnotationView elements array, access to AnnotationDataCollection. Also AnnotationViewCollection class allows to:

search AnnotationView element linked with specified instance of AnnotationData
render all views from a collection on specified System.Windows.Media.DrawingContext object
render all views from a collection on specified VintasoftImage.

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