DotImage does not include a "Point" annotation out of the box. This topic discusses how to create a custom Point annotation in Visual Basic.
First, we create the PointAnnotation class. To make life easier, we will derive from FrameableAnnotation, override OnPaint to draw the cross, and override Grips because we do not want to show any grips when the point is selected. We also add a Point property that returns the center of the annotation, calculated from the Location and Size.
[C#]
using Atalasoft.Imaging.Annotate;
using System.Drawing;
public class PointAnnotation : FrameableAnnotation, IAnnotationPen
{
private System.Drawing.Pen _pen = new Pen(Color.Black);
private PointGrips _grips = new PointGrips();
const int CROSSSIZE = 25;
public new override void Paint(Graphics graphics, PointF offset, PointF scale, float resolution)
{
graphics.TranslateTransform(offset.X, offset.Y);
graphics.ScaleTransform(scale.X, scale.Y);
graphics.DrawLine(_pen, Location.X, Location.Y, Location.X + Size.Width, Location.Y + Size.Height);
graphics.DrawLine(_pen, Location.X, Location.Y + Size.Height, Location.X + Size.Width, Location.Y);
graphics.DrawEllipse(_pen, new RectangleF(Location, Size));
graphics.ResetTransform();
}
public Pen Pen
{
get
{
return _pen;
}
set
{
_pen = Value;
}
}
public PointF Point
{
get
{
return new PointF((Location.X + Location.X + Size.Width) / (double)2,
(Location.Y + Location.Y + Size.Height) / (double)2);
}
set
{
Location = new PointF(Value.X - Size.Width / (double)2, Value.Y - Size.Height / (double)2);
}
}
public PointAnnotation()
{
Size = new SizeF(CROSSSIZE, CROSSSIZE);
this.Resizable = false;
}
public PointAnnotation(PointF point)
{
Size = new SizeF(CROSSSIZE, CROSSSIZE);
this.Point = point;
this.Resizable = false;
}
public override Atalasoft.Imaging.Annotate.AnnotationGrips Grips
{
get
{
return _grips;
}
}
}
[VB.NET]
Imports Atalasoft.Imaging.Annotate
Imports System.Drawing
Public Class PointAnnotation
Inherits FrameableAnnotation
Implements IAnnotationPen
Dim _pen As System.Drawing.Pen = New Pen(Color.Black)
Dim _grips As PointGrips = New PointGrips
Const CROSSSIZE As Integer = 25
Public Overloads Overrides Sub Paint(ByVal graphics As Graphics, ByVal offset As PointF, _
ByVal scale As PointF, _
ByVal resolution As Single)
graphics.TranslateTransform(offset.X, offset.Y)
graphics.ScaleTransform(scale.X, scale.Y)
graphics.DrawLine(_pen, Location.X, Location.Y, Location.X + Size.Width, Location.Y + Size.Height)
graphics.DrawLine(_pen, Location.X, Location.Y + Size.Height, Location.X + Size.Width, Location.Y)
graphics.DrawEllipse(_pen, New RectangleF(Location, Size))
graphics.ResetTransform()
End Sub
Public Property Pen() As Pen Implements Atalasoft.Imaging.Annotate.IAnnotationPen.Pen
Get
Return _pen
End Get
Set(ByVal Value As Pen)
_pen = Value
End Set
End Property
Public Property Point() As PointF
Get
Return New PointF((Location.X + Location.X + Size.Width) / 2, (Location.Y + Location.Y + Size.Height) / 2)
End Get
Set(ByVal Value As PointF)
Location = New PointF(Value.X - Size.Width / 2, Value.Y - Size.Height / 2)
End Set
End Property
Public Sub New()
Size = New SizeF(CROSSSIZE, CROSSSIZE)
Me.Resizable = False
End Sub
Public Sub New(ByVal point As PointF)
Size = New SizeF(CROSSSIZE, CROSSSIZE)
Me.Point = point
Me.Resizable = False
End Sub
Public Overrides ReadOnly Property Grips() As Atalasoft.Imaging.Annotate.AnnotationGrips
Get
Return _grips
End Get
End Property
End Class
Now, in order to create the annotation, we do not want to use the "CreateAnnotation" method since that requires clicking and dragging to interactively position and size. We just want the user to click on the document to place the point. By handling the AnnotationController or AnnotateViewer's MouseDown event, we can simple add the new annotation to the Current Layer. We do have to create a HitTest method that will loop through all annotations and make sure we're not clicking on an existing one. This method will eventually be part of the AnnotationController class.
[C#]
private void AnnotateViewer1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
// place point annotation if we're not clicking on an existing one
if (HitTest(new PointF(e.X, e.Y)) == null)
{
// scale and offset the point
PointF point = new PointF(e.X / (double)this.AnnotateViewer1.Zoom + this.AnnotateViewer1.Location.X,
e.Y / (double)this.AnnotateViewer1.Zoom + this.AnnotateViewer1.Location.Y);
this.AnnotateViewer1.Annotations.CurrentLayer.Add(new PointAnnotation(Point));
}
}
// make our own "HitTest" method to determine if the point is over an annotation
private Annotation HitTest(PointF point)
{
foreach (Layer layer in AnnotateViewer1.Annotations.Layers)
{
foreach (Annotation an in layer)
{
Region reg = an.GetRegion();
if (reg.IsVisible(point.X, point.Y))
return an;
}
}
}
[VB.NET]
Private Sub AnnotateViewer1_MouseDown(ByVal sender As Object, _
ByVal e As System.Windows.Forms.MouseEventArgs) _
Handles AnnotateViewer1.MouseDown
'place point annotation if we're not clicking on an existing one
If HitTest(New PointF(e.X, e.Y)) Is Nothing Then
'scale and offset the point
Dim point As PointF = New PointF(e.X / Me.AnnotateViewer1.Zoom + Me.AnnotateViewer1.Location.X, _
e.Y / Me.AnnotateViewer1.Zoom + Me.AnnotateViewer1.Location.Y)
Me.AnnotateViewer1.Annotations.CurrentLayer.Add(New PointAnnotation(Point))
End If
End Sub
'make our own "HitTest" method to determine if the point is over an annotation
Private Function HitTest(ByVal point As PointF) As Annotation
For Each layer As Layer In AnnotateViewer1.Annotations.Layers
For Each an As Annotation In layer
Dim reg As Region = an.GetRegion()
If reg.IsVisible(point.X, point.Y) Then
Return an
End If
Next
Next
End Function
If you wish to serialize the custom annotation in order to save it to XMP, you will also need to override the ToXmp and FromXmp methods. See the documentation on how to do that.
Original Article:
Q10087 - HOWTO: Create a Custom Point Annotation