How to create custom triangle annotation?

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VintaSoft Annotation .NET Plug-in allows to create any annotation from zero point, that is to create:

A class derived from AnnotationData class with annotation's data.
A class implementing IInteractionController interface and defining how the annotation can be built.
A class implementing IInteractionController interface and defining how the annotation can be transformed.
A class, derived from InteractionPoint class, defining a visual appearance of annotation's interactive points, if necessary.
A class, derived from AnnotationView class, defining annotation's visual appearance as well as how the user can interact with annotation.

Besides others, VintaSoft Annotation .NET Plug-in contains a set of standard annotations and each of them may be used in the capacity of base annotation.

The object of this article is let us review how to create triangle annotation based on polygon annotation. For that it will be necessary to create three classes:

TriangleAnnotationData class derived from PolygonAnnotationData class.
TriangleAnnotationInteractionPoint class derived from InteractionPolygonPoint class.
TriangleAnnotationView class derived from PolygonAnnotationView class.

TriangleAnnotationData class

TriangleAnnotationData class:

Stores annotation's data (coordinates of triangle vertices) - properties of base class.
Serializes annotation's data - constructor of serialization.
Clones annotation's data - Clone method.

Here is an implementation of TriangleAnnotationData class:

VB.NET

Imports System.Drawing
Imports System.Runtime.Serialization
Imports System.Security.Permissions

Imports Vintasoft.Imaging.Annotation

''' <summary>
''' Class that holds information about the annotation that displays a triangle.
''' </summary>
<Serializable> _
Public Class TriangleAnnotationData
        Inherits PolygonAnnotationData

        #Region "Constructors"

        ''' <summary>
        ''' Initializes a new instance of the <see cref="TriangleAnnotationData"/> class.
        ''' </summary>
        Public Sub New()
                MyBase.New()
        End Sub

        ''' <summary>
        ''' Initializes a new instance of the <see cref="TriangleAnnotationData"/> class.
        ''' </summary>
        ''' <param name="info">The SerializationInfo to populate with data.</param>
        ''' <param name="context">The destination for this serialization.</param>
        Public Sub New(info As SerializationInfo, context As StreamingContext)
                MyBase.New(info, context)
                Dim sdkVersion As Integer = 70
                If TypeOf context.Context Is Integer Then
                        sdkVersion = CInt(context.Context)
                End If

                If sdkVersion < 70 Then
                        Dim firstPoint As PointF = CType(info.GetValue("FirstPoint", GetType(PointF)), PointF)
                        Dim secondPoint As PointF = CType(info.GetValue("SecondPoint", GetType(PointF)), PointF)
                        Dim thirdPoint As PointF = CType(info.GetValue("ThirdPoint", GetType(PointF)), PointF)

                        Dim points As PointF() = New PointF() {firstPoint, secondPoint, thirdPoint}
                        Me.Points.ClearAndAddRange(points)

                        '
                        Me.Location = CType(info.GetValue("Location", GetType(PointF)), PointF)

                        Me.FillBrush = New AnnotationSolidBrush(Color.Transparent)
                        Me.Border = True
                        Me.Outline.DashStyle = AnnotationPenDashStyle.Solid
                End If
        End Sub

        #End Region



        #Region "Methods"

        ''' <summary>
        ''' Creates a new object that is a copy of the current instance.
        ''' </summary>
        ''' <returns>A new object that is a copy of this instance.</returns>
        Public Overrides Function Clone() As Object
                Dim result As New TriangleAnnotationData()
                CopyTo(result)
                Return result
        End Function


        #Region "ISerializable Members"

        ''' <summary>
        ''' Populates a SerializationInfo with the data needed to serialize the target object.
        ''' </summary>
        ''' <param name="info">The SerializationInfo to populate with data.</param>
        ''' <param name="context">The destination for this serialization.</param>
        <SecurityPermission(SecurityAction.LinkDemand, Flags := SecurityPermissionFlag.SerializationFormatter)> _
        Public Overrides Sub GetObjectData(info As SerializationInfo, context As StreamingContext)
                If info Is Nothing Then
                        Throw New ArgumentNullException("info")
                End If

                Dim sdkVersion As Integer = 70
                If TypeOf context.Context Is Integer Then
                        sdkVersion = CInt(context.Context)
                End If

                If sdkVersion >= 70 Then
                        MyBase.GetObjectData(info, context)
                Else
                        info.AddValue("Guid", Me.Guid)
                        info.AddValue("CreationTime", Me.CreationTime)
                        info.AddValue("ModifiedTime", Me.ModifiedTime)

                        info.AddValue("Location", Me.Location)
                        info.AddValue("Rotation", Me.Rotation)
                        info.AddValue("Size", Me.Size)
                        info.AddValue("Visible", Me.IsVisible)
                        info.AddValue("HorizontalMirrored", Me.HorizontalMirrored)
                        info.AddValue("VerticalMirrored", Me.VerticalMirrored)

                        info.AddValue("Border", Me.Border)

                        info.AddValue("ZOrder", CInt(0))
                        info.AddValue("BackColor", Color.Black)

                        info.AddValue("Outline", Me.Outline)
                        info.AddValue("ToolTip", Me.ToolTip)

                        If sdkVersion >= 43 Then
                                info.AddValue("Name", Me.Name)
                        End If

                        info.AddValue("FirstPoint", PointF.Empty)
                        info.AddValue("SecondPoint", PointF.Empty)
                        info.AddValue("ThirdPoint", PointF.Empty)
                End If
        End Sub

        #End Region

        #End Region

End Class

using System;
using System.Drawing;
using System.Runtime.Serialization;
using System.Security.Permissions;

using Vintasoft.Imaging.Annotation;

namespace AnnotationDemo
{
    /// <summary>
    /// Class that holds information about the annotation that displays a triangle.
    /// </summary>
    [Serializable]
    public class TriangleAnnotationData : PolygonAnnotationData
    {

        #region Constructors

        /// <summary>
        /// Initializes a new instance of the <see cref="TriangleAnnotationData"/> class.
        /// </summary>
        public TriangleAnnotationData()
            : base()
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="TriangleAnnotationData"/> class.
        /// </summary>
        /// <param name="info">The SerializationInfo to populate with data.</param>
        /// <param name="context">The destination for this serialization.</param>
        public TriangleAnnotationData(SerializationInfo info, StreamingContext context)
            : base(info, context)
        {
            int sdkVersion = 70;
            if (context.Context is int)
                sdkVersion = (int)context.Context;

            if (sdkVersion < 70)
            {
                PointF firstPoint = (PointF)info.GetValue("FirstPoint", typeof(PointF));
                PointF secondPoint = (PointF)info.GetValue("SecondPoint", typeof(PointF));
                PointF thirdPoint = (PointF)info.GetValue("ThirdPoint", typeof(PointF));

                PointF[] points = new PointF[] { firstPoint, secondPoint, thirdPoint };
                this.Points.ClearAndAddRange(points);

                //
                this.Location = (PointF)info.GetValue("Location", typeof(PointF));

                this.FillBrush = new AnnotationSolidBrush(Color.Transparent);
                this.Border = true;
                this.Outline.DashStyle = AnnotationPenDashStyle.Solid;
            }
        }

        #endregion



        #region Methods

        /// <summary>
        /// Creates a new object that is a copy of the current instance.
        /// </summary>
        /// <returns>A new object that is a copy of this instance.</returns>
        public override object Clone()
        {
            TriangleAnnotationData result = new TriangleAnnotationData();
            CopyTo(result);
            return result;
        }


        #region ISerializable Members

        /// <summary>
        /// Populates a SerializationInfo with the data needed to serialize the target object.
        /// </summary>
        /// <param name="info">The SerializationInfo to populate with data.</param>
        /// <param name="context">The destination for this serialization.</param>
        [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.SerializationFormatter)]
        public override void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            if (info == null)
                throw new ArgumentNullException("info");

            int sdkVersion = 70;
            if (context.Context is int)
                sdkVersion = (int)context.Context;

            if (sdkVersion >= 70)
            {
                base.GetObjectData(info, context);
            }
            else
            {
                info.AddValue("Guid", this.Guid);
                info.AddValue("CreationTime", this.CreationTime);
                info.AddValue("ModifiedTime", this.ModifiedTime);

                info.AddValue("Location", this.Location);
                info.AddValue("Rotation", this.Rotation);
                info.AddValue("Size", this.Size);
                info.AddValue("Visible", this.IsVisible);
                info.AddValue("HorizontalMirrored", this.HorizontalMirrored);
                info.AddValue("VerticalMirrored", this.VerticalMirrored);

                info.AddValue("Border", this.Border);

                info.AddValue("ZOrder", (int)0);
                info.AddValue("BackColor", Color.Black);

                info.AddValue("Outline", this.Outline);
                info.AddValue("ToolTip", this.ToolTip);

                if (sdkVersion >= 43)
                    info.AddValue("Name", this.Name);

                info.AddValue("FirstPoint", PointF.Empty);
                info.AddValue("SecondPoint", PointF.Empty);
                info.AddValue("ThirdPoint", PointF.Empty);
            }
        }

        #endregion

        #endregion

    }
}

TriangleAnnotationInteractionPoint class

TriangleAnnotationInteractionPoint class could have been not implemented, but we had decided to change the appearance of triangle vertices and after that it was realized.
TriangleAnnotationInteractionPoint class:

Defines the appearance of triangle vertices - the vertex will be drawn as large red circle - constructor of class.
Draws a vertex of rectangle - Draw method.
Clones a vertex of rectangle Clone - method.

Here is an implementation of TriangleAnnotationInteractionPoint class:

VB.NET

Imports System.Drawing

Imports Vintasoft.Imaging
Imports Vintasoft.Imaging.UI.VisualTools.UserInteraction
Imports Vintasoft.Imaging.UI

''' <summary>
''' Represents rounded interaction point for vertices of triangle annotation.
''' </summary>
Friend Class TriangleAnnotationInteractionPoint
        Inherits InteractionPolygonPoint

        #Region "Constructors"

        ''' <summary>
        ''' Initializes a new instance of the <see cref="TriangleAnnotationInteractionPoint"/> class.
        ''' </summary>
        Friend Sub New()
                MyBase.New("Resize")
                BorderColor = Color.Black
                FillColor = Color.FromArgb(100, Color.Red)
                Radius = 6
        End Sub

        #End Region



        #Region "Methods"

        ''' <summary>
        ''' Draws the interaction area on specified graphics.
        ''' </summary>
        ''' <param name="viewer">The image viewer.</param>
        ''' <param name="g">The graphics to draw the interaction area.</param>
        Public Overrides Sub Draw(viewer As ImageViewer, g As Graphics)
                Dim rect As RectangleF = GetDrawingRect()

                If FillBrush IsNot Nothing Then
                        g.FillEllipse(FillBrush, rect)
                End If
                If BorderPen IsNot Nothing Then
                        g.DrawEllipse(BorderPen, rect)
                End If
        End Sub

        ''' <summary>
        ''' Creates a new object that is a copy of the current instance.
        ''' </summary>
        ''' <returns>A new object that is a copy of this instance.</returns>
        Public Overrides Function Clone() As InteractionArea
                Dim area As New TriangleAnnotationInteractionPoint()
                CopyTo(area)
                Return area
        End Function

        #End Region

End Class

using System.Drawing;

using Vintasoft.Imaging;
using Vintasoft.Imaging.UI.VisualTools.UserInteraction;
using Vintasoft.Imaging.UI;

namespace AnnotationDemo
{
    /// <summary>
    /// Represents rounded interaction point for vertices of triangle annotation.
    /// </summary>
    internal class TriangleAnnotationInteractionPoint : InteractionPolygonPoint
    {

        #region Constructors

        /// <summary>
        /// Initializes a new instance of the <see cref="TriangleAnnotationInteractionPoint"/> class.
        /// </summary>
        internal TriangleAnnotationInteractionPoint()
            : base("Resize")
        {
            BorderColor = Color.Black;
            FillColor = Color.FromArgb(100, Color.Red);
            Radius = 6;
        }

        #endregion



        #region Methods

        /// <summary>
        /// Draws the interaction area on specified graphics.
        /// </summary>
        /// <param name="viewer">The image viewer.</param>
        /// <param name="g">The graphics to draw the interaction area.</param>
        public override void Draw(ImageViewer viewer, Graphics g)
        {
            RectangleF rect = GetDrawingRect();

            if (FillBrush != null)
                g.FillEllipse(FillBrush, rect);
            if (BorderPen != null)
                g.DrawEllipse(BorderPen, rect);
        }

        /// <summary>
        /// Creates a new object that is a copy of the current instance.
        /// </summary>
        /// <returns>A new object that is a copy of this instance.</returns>
        public override InteractionArea Clone()
        {
            TriangleAnnotationInteractionPoint area = new TriangleAnnotationInteractionPoint();
            CopyTo(area);
            return area;
        }

        #endregion

    }
}

TriangleAnnotationView class

TriangleAnnotationView class:

Determines that for annotation building is necessary to use standard point based transformer, the object should contain 3 points - constructor of class.
Determines that for transforming annotation as rectangle is necessary to use standard rectangle based transformer - constructor of class.
Determines that for transforming of annotation as a set of points is necessary to use standard point based transformer, for drawing of vertices should be used TriangleAnnotationInteractionPoint class - constructor of class.
Clones annotation's appearance - Clone method.

Here is an implementation of TriangleAnnotationView class:

VB.NET

Imports System.Drawing

Imports Vintasoft.Imaging.Annotation
Imports Vintasoft.Imaging.Annotation.UI
Imports Vintasoft.Imaging.Annotation.UI.VisualTools.UserInteraction

''' <summary>
''' Class that determines how to display the annotation that displays a triangle
''' and how user can interact with annotation.
''' </summary>
Public Class TriangleAnnotationView
        Inherits PolygonAnnotationView

        #Region "Constructors"

        ''' <summary>
        ''' Initializes a new instance of the <see cref="TriangleAnnotationView"/> class.
        ''' </summary>
        ''' <param name="annotationData">Object that stores the annotation data.</param>
        Public Sub New(annotationData As TriangleAnnotationData)
                MyBase.New(annotationData)
                FillBrush = Nothing

                ' create a point-based builder
                Builder = New PointBasedAnnotationPointBuilder(Me, 3, 3)

                ' create a transformer for rectangular mode
                Dim rectangleTransformer As New PointBasedAnnotationRectangularTransformer(Me)
                ' show bounding box area
                rectangleTransformer.BoundingBoxArea.IsVisible = True
                RectangularTransformer = rectangleTransformer

                ' create a transformer for point mode
                Dim pointsTransformer As New PointBasedAnnotationPointTransformer(Me)
                ' change interaction points color
                pointsTransformer.InteractionPointBackColor = Color.FromArgb(100, Color.Red)
                pointsTransformer.SelectedInteractionPointBackColor = Color.FromArgb(150, Color.Red)
                ' change interaction points type
                pointsTransformer.PolygonPointTemplate = New TriangleAnnotationInteractionPoint()
                PointTransformer = pointsTransformer

                GripMode = GripMode.RectangularAndPoints
        End Sub

        #End Region



        #Region "Methods"

        ''' <summary>
        ''' Creates a new object that is a copy of the current
        ''' <see cref="TriangleAnnotationView"/> instance.
        ''' </summary>
        ''' <returns>A new object that is a copy of this <see cref="TriangleAnnotationView"/>
        ''' instance.</returns>
        Public Overrides Function Clone() As Object
                Return New TriangleAnnotationView(DirectCast(Me.Data.Clone(), TriangleAnnotationData))
        End Function

        #End Region

End Class

using System.Drawing;

using Vintasoft.Imaging.Annotation;
using Vintasoft.Imaging.Annotation.UI;
using Vintasoft.Imaging.Annotation.UI.VisualTools.UserInteraction;

namespace AnnotationDemo
{
    /// <summary>
    /// Class that determines how to display the annotation that displays a triangle
    /// and how user can interact with annotation.
    /// </summary>
    public class TriangleAnnotationView : PolygonAnnotationView
    {

        #region Constructors

        /// <summary>
        /// Initializes a new instance of the <see cref="TriangleAnnotationView"/> class.
        /// </summary>
        /// <param name="annotationData">Object that stores the annotation data.</param>
        public TriangleAnnotationView(TriangleAnnotationData annotationData)
            : base(annotationData)
        {
            FillBrush = null;

            // create a point-based builder
            Builder = new PointBasedAnnotationPointBuilder(this, 3, 3);

            // create a transformer for rectangular mode
            PointBasedAnnotationRectangularTransformer rectangleTransformer = new PointBasedAnnotationRectangularTransformer(this);
            // show bounding box area
            rectangleTransformer.BoundingBoxArea.IsVisible = true;
            RectangularTransformer = rectangleTransformer;

            // create a transformer for point mode
            PointBasedAnnotationPointTransformer pointsTransformer = new PointBasedAnnotationPointTransformer(this);
            // change interaction points color
            pointsTransformer.InteractionPointBackColor = Color.FromArgb(100, Color.Red);
            pointsTransformer.SelectedInteractionPointBackColor = Color.FromArgb(150, Color.Red);
            // change interaction points type
            pointsTransformer.PolygonPointTemplate = new TriangleAnnotationInteractionPoint();
            PointTransformer = pointsTransformer;

            GripMode = GripMode.RectangularAndPoints;                
        }

        #endregion



        #region Methods

        /// <summary>
        /// Creates a new object that is a copy of the current
        /// <see cref="TriangleAnnotationView"/> instance.
        /// </summary>
        /// <returns>A new object that is a copy of this <see cref="TriangleAnnotationView"/>
        /// instance.</returns>
        public override object Clone()
        {
            return new TriangleAnnotationView((TriangleAnnotationData)this.Data.Clone());
        }

        #endregion

    }
}

Registering link between TriangleAnnotationData and TriangleAnnotationView classes

Link between TriangleAnnotationData and TriangleAnnotationView classes should be registered before any instance of TriangleAnnotationView class will be created. Link between TriangleAnnotationData and TriangleAnnotationView classes can be registered using the AnnotationViewFactory.RegisterViewForAnnotationData method.

The implementation of triangle annotation in C# and VB.NET is a part of AnnotationDemo project code.

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