How to implement a Magnifying Glass with DicomObjects

It is possible to implement a magnifying glass tool in DicomObjects.NET.This functionality can be achieved by using a second DicomImage which is a copy of the original image (scaled, zoomed and scrolled accordingly) and overlaying onto the original image.

Because the new image is a “Clone” of the original, it shares the same underlying DataSet, and it therefore uses negligible memory and takes a tiny amount of time to create.

The mouse cursor can be used to control the position of the magnifying glass easily thanks to the DicomViewer Mouse events.

The Magnifying glass (referred to as ZoomImage in the following code) can be initialised through the DicomViewer Mouse Down event.

DicomObjects.NET

private void EndMagnifier()
{
  if (MagnifierImage != null)
  {
   Viewer.Images.Remove(MagnifierImage);
   MagnifierImage = null;
  }
}

private void SetMagnifier(Point p)
{
  if (ActiveImage != null)
  {
	if (MagnifierImage == null)
	{
	  MagnifierImage = ActiveImage.Clone(true) as DicomImage;
	  MagnifierImage.StretchMode = StretchModes.NoStretch;
	  Viewer.Images.Add(MagnifierImage);
	  MagnifierImage.Zoom = DicomGlobal.Zoom(ActiveImage.Matrix(Viewer)) * 2;
	  MagnifierImage.Labels.Clear();
	}

	float MagnifierSize = 0.2F;
	RectangleF Rect = new RectangleF(p.X / (float)Viewer.ClientSize.Width, 
		p.Y / (float)Viewer.ClientSize.Height, 0, 0);
	Rect.Inflate(MagnifierSize / 2, MagnifierSize / 2);
	MagnifierImage.Area = Rect;
	// Work out how far to scroll the magnified image 
	// by doing screen ==> Image==> Screen image coordinates
	// not simply done by scaling of offset, as anisometropic pixels can cause problems
	var ImageCoords = ActiveImage.ScreenToImage(p, Viewer).Value;
	var MagCoords = MagnifierImage.ImageToScreen(ImageCoords, Viewer).Value;
	MagnifierImage.Scroll = ((PointF)p) + new SizeF((MagnifierImage.Scroll - new SizeF(MagCoords)));
   }
}

private void Viewer_MouseDown(object sender, MouseEventArgs e)
{
	Viewer.Focus();
	SetMagnifier(e.Location);	
}

private void Viewer_MouseMove(object sender, MouseEventArgs e)
{
	SetMagnifier(e.Position);
}

private void Viewer_MouseUp(object sender, MouseEventArgs e)
{
	EndMagnifier();
}

Download the CSharp Sample Viewer Program to try the Magnifying glass.

DicomObjects.COM

    
Sub SetMagnifier(ByVal X As Single, ByVal Y As Single)

    Const MagnifierSize = 100
    Dim x1 As Single, y1 As Single

    If Not ActiveImage Is Nothing Then
        If MagnifierImage Is Nothing Then
            Viewer.AutoDisplay = False
            Viewer.Images.Add ActiveImage
            Viewer.AutoDisplay = True
            Set MagnifierImage = Viewer.Images(Viewer.Images.Count)
            MagnifierImage.StretchMode = NoStretch
            MagnifierImage.Zoom = ActiveImage.ActualZoom * 2
            MagnifierImage.Labels.Clear
        End If

        If Viewer.ImageIndex(X, Y) <> 0 Then

            ' image coordinates
            x1 = Viewer.ImageXPosition(X, Y)
            y1 = Viewer.ImageYPosition(X, Y)

            MagnifierImage.ScrollX = x1 * MagnifierImage.ActualZoom - MagnifierSize / 2
            MagnifierImage.ScrollY = y1 * MagnifierImage.ActualZoom - MagnifierSize / 2

            'now move the magnify viewer within the main viewer
            MagnifierImage.Left = (X - MagnifierSize / 2) * 1000 / Viewer.Width
            MagnifierImage.Top = (Y - MagnifierSize / 2) * 1000 / Viewer.Height
            MagnifierImage.Right = (X + MagnifierSize / 2) * 1000 / Viewer.Width
            MagnifierImage.Bottom = (Y + MagnifierSize / 2) * 1000 / Viewer.Height

        End If
    End If
End Sub

Sub EndMagnifier()
	If Not MagnifierImage Is Nothing Then
		Viewer.Images.Remove Viewer.Images.IndexOf(MagnifierImage)
		Set MagnifierImage = Nothing
		Viewer.Refresh
	End If
End Sub

Private Sub Viewer_MouseDown(Button As Integer, Shift As Integer, X As Long, Y As Long)
	SetMagnifier X, Y    
	LastPositionX = X
	LastPositionY = Y
End Sub

Private Sub Viewer_MouseMove(Button As Integer, Shift As Integer, X As Long, Y As Long)
	SetMagnifier X, Y	  
	LastPositionX = X
	LastPositionY = Y
End Sub

Private Sub Viewer_MouseUp(Button As Integer, Shift As Integer, X As Long, Y As Long)
	EndMagnifier
End Sub

Download the VB6 Sample Viewer Program to try the Magnifying glass.