The building of annotation is performed by annotation builder, the transformation of annotation is performed by annotation transformer. The visual tool gets information about builder and transformer from WpfAnnotationView class:

• WpfAnnotationView.Builder - defines the interactive controller, which must be used for building of annotation.
• WpfAnnotationView.Transformer - defines the interactive controller, which must be used for transformation of annotation.
• WpfAnnotationView.InteractionController - defines the current interactive controller.

Build annotation in WPF annotation viewer

For newly created annotation the value of WpfAnnotationView.InteractionController property is equal to the value of WpfAnnotationView.Builder property, i.e. annotation is ready for building.
The WpfAnnotationVisualTool.AddAndBuildAnnotation method allows to start the annotation building process, i.e. method adds the annotation into the annotation collection of focused image, gets the current interaction controller (builder) using WpfAnnotationView.InteractionController property and starts the building of annotation.
For annotation building can be used the following interaction controllers (builders):

• WpfRectangularAnnotationBuilder - the builder for rectangular-based annotations
• WpfPointBasedAnnotationFreehandBuilder - the builder for point-based annotations, which builds freehand annotation.
• WpfPointBasedAnnotationLineBuilder - the builder for point-based annotations, which builds line annotation.
• WpfPointBasedAnnotationPointBuilder - the builder for point-based annotations, which builds lines annotation.

Transform annotation in WPF annotation viewer

Transformation of annotation, which is focused in WpfAnnotationViewer, can be started using mouse. For annotation transformation can be used the following interactive controllers:

• WpfRectangularAnnotationTransformer - the transformer of rectangular annotations. Implements relocation, size change, rotation of annotation.
• WpfRectangularTextAnnotationTransformer - the transformer of rectangular annotations implementing IWpfRectangularTextAnnotation interface, which defines rectangular annotation containing Text property of string type. That transformer can be derived from WpfRectangularTextAnnotationTransformer and extends its functionality, providing the window for editing text of annotation.
• WpfPointBasedAnnotationPointTransformer - the transformer for point-based annotations. Implements marking and repositioning of annotation's points.
• WpfPointBasedAnnotationRectangularTransformer - the transformer for point-based annotations. Transforms annotation using its bounding rectangle. Implements relocation, size change, rotation of annotation.

Transform annotation using several controllers

The WpfCompositeInteractionController class allows to combine several interactive controllers.

For example, WpfFreeTextAnnotationView uses composite interaction controller because WpfFreeTextAnnotationView consists from 2 annotations (WpfTextAnnotationView and WpfLeaderLineAnnotationView) and needs to interact with both annotations using different interactive controllers:

• WpfRectangularAnnotationTransformer transforms WpfTextAnnotationView
• WpfPointBasedAnnotationPointTransformer transforms WpfLeaderLineAnnotationView
• WpfRectangularAnnotationTransformer transforms WpfCompositeAnnotationView (the entire annotation)