Bifocal Lens

Download a sample VB program that creates a bifocal lens where objects in the focal region are larger than those outside the focal region.

Instructions for Creating the Example:

1. Start Visual Basic from the Start menu.
2. Select Standard EXE, and click Open.
3. Find 8 pictures and name them picture1.jpg - picture8.jpg.  You can use the 8 provided in the download zip file.
4. Download a double slider control and save it in your project's directory.
5. Draw two picture boxes on your form, name them picDivider(0) and picDivider(1) - these are a control array, to get the index number just set the Index property - and set finally their BackColor to red.
6. Draw one image box on your form and set its Index property to 0.
7. Add the double slider to your project by going to the Add User Control item in the menu shown below.

8. In the dialog box that appears, click on the Existing tab, then find the file RangeTool.ctl
9. An icon will now appear in your toolbox for the double slider.  Draw a double slider on your form.
10. Draw a line on your form as shown in the picture below.

11. Add the following code and you should have a bifocal lens:

Dim RegularWidth As Integer
Dim NarrowWidth As Integer

Private Sub Form_Load()
    ' define widths for objects within each focal area
    RegularWidth = 1815
    NarrowWidth = RegularWidth / 4

    ' start up random number generator
    Randomize

    ' set the range of the double slider to be the full range of the form
    RangeTool1.Max = Me.ScaleWidth
    RangeTool1.Min = 0
    RangeTool1.UpperValue = Me.ScaleWidth - 200

    ' place the focal dividing bars
    picDivider(0).Left = RangeTool1.LowerValue
    picDivider(1).Left = RangeTool1.UpperValue

    ' load some pictures and position them randomly
    For i = 1 To 8
        Load Image1(i)
        FileName = App.Path & "\picture" & i & ".jpg"
        Image1(i).Picture = LoadPicture(FileName)
        Image1(i).Left = Rnd * (Me.ScaleWidth - Image1(i).Width)
        Image1(i).Top = Rnd * (Line1.Y1 - Image1(i).Height)
        Image1(i).Visible = True
    Next

    ' set the initial size of all the pictures
    Call RangeTool1_Scroll

End Sub



Private Sub RangeTool1_Scroll()
    ' move the focal dividing bars
    picDivider(0).Left = RangeTool1.LowerValue
    picDivider(1).Left = RangeTool1.UpperValue

    ' resize pictures inside the focal region to be larger
    For i = 1 To 8
        If Image1(i).Left > picDivider(0).Left And Image1(i).Left < picDivider(1).Left Then
            Image1(i).Width = RegularWidth
        Else
            Image1(i).Width = NarrowWidth
        End If
    Next
End Sub