Calculate Overlap Between Fields

Question / Problem: 

How do I calculate the overlap between fields?

Answer / Solution: 

The functions below calculate the 2 dimensional and horizontal overlap of two rectangles as a value from 0 to 1:

Public Function FieldOverlapHoriz(a As Object, b As Object) As Double
   If a.PageIndex <> b.PageIndex Or a.PageIndex = -1 Then  Exit Function
   Dim overlap As Double
   overlap = Max((Min(a.Left + a.Width, b.Left + b.Width) - Max(a.Left, b.Left)), 0)
   FieldOverlapHoriz = overlap / Min(a.Width, b.Width)
End Function

Public Function FieldOverlap2D(a As Object, b As Object) As Double
   'returns percentage overlap of two fields, subfields or
   ' alternatives (0.0 if no overlap, 1.0 if perfect overlap)
   FieldOverlap = 0
   'Check if fields are on the same page and that both exist
   If a.PageIndex <> b.PageIndex Or a.PageIndex = -1 Then  Exit Function
   Dim overlapArea As Double
   overlapArea = Max((Min(a.Left + a.Width, b.Left + b.Width) - Max(a.Left, b.Left)), 0) _
                 * Max((Min(a.Top + a.Height, b.Top + b.Height) - Max(a.Top, b.Top)), 0)
   FieldOverlap2D = overlapArea / Max(a.Width * a.Height, b.Width * b.Height)
End Function

Private Function Max(v1 As Long, v2 As Long) As Long
   If v1 > v2 Then Max = v1 Else Max = v2
End Function

Private Function Min(v1 As Long, v2 As Long) As Long
   If v1 < v2 Then Min = v1 Else Min = v2
End Function

Applies to: