Advanced Magnifying Glass

Take the following steps to create a project that uses advanced features of the Magnifying Glass:

Start Visual Studio .NET.
Open the project that you created in the tutorial, Using the Magnifying Glass.
Switch to Form1 code view (right-click Form1 in the solution explorer then select View Code ) and add the following lines at the beginning of the file (after the existing Imports / using statements):
[Visual Basic]
```
 
Imports System.Drawing.Drawing2D 
```
[C#]
```
using System.Drawing.Drawing2D; 
```

Add the following code to derive your own class from RasterMagnifyGlass, and override OnPaintBorder, OnPaintCrosshair and OnPaintImage. For Visual Basic, put this code at the end of the file. For #, put this code just inside the namespace.

[Visual Basic]


' My own class, derived from Leadtools.WinForms.RasterMagnifyGlass
Public Class MyMagGlass
   Inherits RasterMagnifyGlass

   Protected Overrides Sub OnPaintBorder(ByVal g As Graphics, ByVal centerPoint As Point)
      g.DrawEllipse(Pens.Blue, centerPoint.X - CInt(Me.Size.Width / 2), centerPoint.Y - CInt(Size.Height / 2), Size.Width - 1, Size.Height - 1)
   End Sub

   Protected Overrides Sub OnPaintCrosshair(ByVal g As Graphics, ByVal centerPoint As Point)
      g.DrawRectangle(Pens.Red, centerPoint.X - 10, centerPoint.Y - 10, 20, 20)
   End Sub

   Protected Overrides Sub OnPaintImage(ByVal g As Graphics, ByVal centerPoint As Point)
      Dim t As New Transformer(Viewer.Transform)
      Dim rcDst As New Rectangle(centerPoint.X - (Size.Width / 2), centerPoint.Y - (Size.Height / 2), Size.Width - 1, Size.Height - 1)
      Dim rcSrc As Rectangle = Rectangle.Round(t.RectangleToLogical(New RectangleF(rcDst.Left, rcDst.Top, rcDst.Width, rcDst.Height)))

      Dim gstate As GraphicsState = g.Save()

      Dim path As New GraphicsPath
      path.AddEllipse(rcDst)
      Dim rgn = New Region(path)
      path.Dispose()

      Viewer.Image.DisableEvents()
      Dim contrast As Integer = Viewer.Image.PaintContrast
      Viewer.Image.PaintContrast = 1000

      g.Clip = rgn
      Viewer.Image.Paint(g, rcSrc, rcSrc, rcDst, rcDst, Viewer.PaintProperties)
      Viewer.Image.PaintContrast = contrast
      Viewer.Image.EnableEvents()

      g.Restore(gstate)
      rgn.Dispose()
   End Sub

[C#]


            
// My own class, derived from Leadtools.WinForms.RasterMagnifyGlass
public class MyMagGlass : RasterMagnifyGlass
{
   protected override void OnPaintBorder(Graphics g, Point centerPoint)
   {
      g.DrawEllipse(Pens.Blue, centerPoint.X-(Size.Width/2), centerPoint.Y-(Size.Height/2), Size.Width-1, Size.Height-1);
   }

   protected override void OnPaintCrosshair(Graphics g, Point centerPoint)
   {
      g.DrawRectangle(Pens.Red, centerPoint.X-10, centerPoint.Y-10, 20, 20);
   }

   protected override void OnPaintImage(Graphics g, Point centerPoint)
   {
      Transformer t = new Transformer(Viewer.Transform);
      Rectangle rcDst = new Rectangle(centerPoint.X-(Size.Width/2), centerPoint.Y-(Size.Height/2), Size.Width-1, Size.Height-1);
      Rectangle rcSrc = Rectangle.Round(t.RectangleToLogical(rcDst));

      GraphicsState gstate = g.Save();

      GraphicsPath path = new GraphicsPath();
      path.AddEllipse(rcDst);
      Region rgn = new Region(path);
      path.Dispose();

      Viewer.Image.DisableEvents();
      int contrast = Viewer.Image.PaintContrast;
      Viewer.Image.PaintContrast = 1000;

      g.Clip = rgn;
      Viewer.Image.Paint(g, rcSrc, rcSrc, rcDst, rcDst, Viewer.PaintProperties);  
      Viewer.Image.PaintContrast = contrast;
      Viewer.Image.EnableEvents();

      g.Restore(gstate);
      rgn.Dispose();
   }
}

In the code for the Load event for Form1, add the following line, just before the line that sets the InteractiveMode property:

[Visual Basic]

 
RasterImageViewer1.MagnifyGlass = New MyMagGlass 'set the MagGlass

[C#]

 
rasterImageViewer1.MagnifyGlass = new MyMagGlass(); //set the MagGlass to my derived class

Build, and Run the program to test it.

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Advanced Magnifying Glass