There may be times when you need to find the section of an image that is currently being viewed by the end user while viweing in one of our windows forms viewers such as WorkspaceViewer, AnnotateViewer or ImageViewer. To do this, you need to check the ScrollPosition, ClientSize and Zoom properties of the viewer.

Here is an example:

[C#]

// Get the viewable area of an image. 
int width = Convert.ToInt32(Math.Min((this.workspaceViewer1.ClientSize.Width / this.workspaceViewer1.Zoom),
                                     (this.workspaceViewer1.Image.Width / this.workspaceViewer1.Zoom))); 
int height = Convert.ToInt32(Math.Min((this.workspaceViewer1.ClientSize.Height / this.workspaceViewer1.Zoom),
                                      (this.workspaceViewer1.Image.Height / this.workspaceViewer1.Zoom))); 
int left = Convert.ToInt32(Math.Abs(this.workspaceViewer1.ScrollPosition.X) / this.workspaceViewer1.Zoom); 
int top = Convert.ToInt32(Math.Abs(this.workspaceViewer1.ScrollPosition.Y) / this.workspaceViewer1.Zoom); 
Rectangle rc = new Rectangle(left, top, width, height); 

[Visual Basic]

' Get the viewable area of an image. 
Dim width As Integer = Convert.ToInt32(Math.Min((Me.workspaceViewer1.ClientSize.Width / Me.workspaceViewer1.Zoom), _
                                                (Me.workspaceViewer1.Image.Width / Me.workspaceViewer1.Zoom))) 
Dim height As Integer = Convert.ToInt32(Math.Min((Me.workspaceViewer1.ClientSize.Height / Me.workspaceViewer1.Zoom), _
                                                 (Me.workspaceViewer1.Image.Height / Me.workspaceViewer1.Zoom))) 
Dim left As Integer = Convert.ToInt32(Math.Abs(Me.workspaceViewer1.ScrollPosition.X) / Me.workspaceViewer1.Zoom) 
Dim top As Integer = Convert.ToInt32(Math.Abs(Me.workspaceViewer1.ScrollPosition.Y) / Me.workspaceViewer1.Zoom) 
Dim rc As Rectangle = New Rectangle(left,top,width,height)

Original Article:

Q10070 - HOWTO: Find the viewable rectangle of an image using DotImage