An example function to crop an existing image based on parameterised points

Private Function CropImage(ByVal OriginalImage As Bitmap, ByVal TopLeft As Point, ByVal BottomRight As Point) As Bitmap  
     Dim btmCropped As New Bitmap((BottomRight.Y - TopLeft.Y), (BottomRight.X - TopLeft.X))  
       Dim grpOriginal As Graphics = Graphics.FromImage(btmCropped)  
      
        grpOriginal.DrawImage(OriginalImage, New Rectangle(0, 0, btmCropped.Width, btmCropped.Height), _  
            TopLeft.X, TopLeft.Y, btmCropped.Width, btmCropped.Height, GraphicsUnit.Pixel)  
        grpOriginal.Dispose()  
      
        Return btmCropped  
   End Function 

Example usage:

   1. Dim bmpImage As New Bitmap("c:\point.jpg") 
   2. bmpImage = CropImage(bmpImage, New Point(0, 0), New Point(100, 100))