privatevoiddicomViewer1_MouseDown(objectsender,MouseEventArgse)
{
	// last mouse position for the zoom operation
	LastXforZoom=e.X;
	LastYforZoom=e.Y;
}

privatevoidtrackBar1_Scroll(objectsender,EventArgse)
{
	PointReferencePoint;

	// calculate the Image Coordinates of 
	// the user-clicked point or centre as required
	ReferencePoint=radioButton1.Checked?newPoint(LastXforZoom,LastYforZoom):
		newPoint(dicomViewer1.Width/2,dicomViewer1.Height/2);
	
	//1)find the image coordinates of the reference point(held in single item array pts)
	Point[]pts=new[]{ReferencePoint};
	System.Drawing.Drawing2D.Matrixmx;
	
	//2)use an inverted copy of the Matrix to go from screen to image space
	mx=dicomViewer1.CurrentImage.Matrix(dicomViewer1);
	mx.Invert();
	mx.TransformPoints(pts);
	
	//3)change Image Zoom
	// An arbitrary calculation to give a reasonable exponential zoom range
	dicomViewer1.CurrentImage.Zoom=(float)(1+(trackBar1.Value-11)*0.125);
	
	//4)apply new Image Matrix to calculate Screen Coordinates of the reference point
	// transforming image back to screen, using the new modified Matrix
	System.Drawing.Drawing2D.Matrixmx2;
	mx2=dicomViewer1.CurrentImage.Matrix(dicomViewer1);
	mx2.TransformPoints(pts);
	
	//5)Calculate offset to modify Image's Scroll property 
	// to leave Reference point unchanged on the screen
	SizeAdjustment=newSize(pts[0])-newSize(ReferencePoint);
	dicomViewer1.CurrentImage.Scroll-=Adjustment;
}

privatevoidForm1_Load(objectsender,EventArgse)
{
	OpenFileDialogd=newOpenFileDialog();
	if(d.ShowDialog()==DialogResult.OK)
	{
		dicomViewer1.Images.Read(d.FileName);
		dicomViewer1.CurrentImage.StretchMode=DicomObjects.Enums.StretchModes.None;
	}
}

  
Dim xinit As Integer, yinit As Integer, Origzoom As Single
Dim LastMouseX As Integer, LastMouseY As Integer

Private Sub Command1_Click()
    CommonDialog1.ShowOpen
    DicomViewer1.Images.ReadFile CommonDialog1.FileName
    DicomViewer1.CurrentImage.StretchToFit = False
    DicomViewer1.CurrentImage.Zoom = 1
End Sub

Private Sub DicomViewer1_MouseDown(Button As Integer, Shift As Integer, x As Long, y As Long)
    LastMouseX = x
    LastMouseY = y
End Sub

Private Sub Slider1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
	xinit = DicomViewer1.CurrentImage.ActualScrollX
	yinit = DicomViewer1.CurrentImage.ActualScrollY
	' set up initial zoom values here
	Origzoom = DicomViewer1.CurrentImage.ActualZoom	
End Sub

Private Sub Slider1_Scroll()
	Dim Image As DicomImage, oldzoom As Single, newzoom As Single
	Dim CentreX As Integer, CentreY As Integer
	Set Image = DicomViewer1.CurrentImage
	newzoom = 2 ^ (Slider1 / 4)
	oldzoom = Image.ActualZoom ' this allows for a stretched to fit image also    
	If ImageCentre Then
		CentreX = DicomViewer1.Width / 2
		CentreY = DicomViewer1.Height / 2
	Else
		CentreX = LastMouseX
		CentreY = LastMouseY
	End If
	
	Image.ShowUpdates = False 'prevent multiple updates
	Image.Zoom = newzoom
	Image.ScrollX = xinit - (CentreX + xinit) * (1 - Image.Zoom / Origzoom)
	Image.ScrollY = yinit - (CentreY + yinit) * (1 - Image.Zoom / Origzoom)
	Image.StretchToFit = False
	Image.ShowUpdates = True
End Sub