The attached source code project draws spline curves
between two points. Its a cubic spline fitting means program start drawing curve
after four clicks.
To run the project, download and unzip the attached file, build and run the
project and click on the form.
![draws-spline-curves.jpg]()
Main source code:
Public
Structure point
Public x As
Integer
Public y As
Integer
Public Sub setxy(ByVal
i As
Integer, ByVal j
As Integer)
x = i
y = j
End Sub
'setxy
Public
Sub clearxy()
x = 0
y = 0
End Sub
'clearxy
End
Structure
'point
Sub
BSPLINE(ByVal p1
As Point,
ByVal p2 As Point,
ByVal p3 As
Point, ByVal p4
As Point,
ByVal divisions As
Integer)
Dim a(4) As
Double
Dim b(4) As
Double
a(0) = (-p1.x + 3 * p2.x - 3 * p3.x + p4.x) / 6.0
a(1) = (3 * p1.x - 6 * p2.x + 3 * p3.x) / 6.0
a(2) = (-3 * p1.x + 3 * p3.x) / 6.0
a(3) = (p1.x + 4 * p2.x + p3.x) / 6.0
b(0) = (-p1.y + 3 * p2.y - 3 * p3.y + p4.y) / 6.0
b(1) = (3 * p1.y - 6 * p2.y + 3 * p3.y) / 6.0
b(2) = (-3 * p1.y + 3 * p3.y) / 6.0
b(3) = (p1.y + 4 * p2.y + p3.y) / 6.0
spline_out_x(0) = a(3)
spline_out_y(0) = b(3)
Dim i As
Integer
For i = 1 To divisions - 1
Dim t As
Single
t = CSng(i) /
CSng(divisions)
spline_out_x(i) = a(3) + t * (a(2) + t * (a(1) + t * a(0)))
spline_out_y(i) = b(3) + t * (b(2) + t * (b(1) + t * b(0)))
Next i
End
Sub
'BSPLINE
Public
Sub plus_draw(ByVal
x As
Integer, ByVal y
As Integer,
ByVal pen_width
As Integer,
ByVal cl As
Color)
Dim g As
Graphics = Graphics.FromHwnd(Me.Handle)
g.DrawLine(New
Pen(cl, pen_width), x - 3, y, x + 3, y)
g.DrawLine(New Pen(cl, pen_width), x, y -
3, x, y + 3)
End
Sub 'plus_draw
Public
Sub Form_MouseUp(ByVal
sender As
Object, ByVal e
As System.Windows.Forms.MouseEventArgs)
If Movement_Click > 3
Then
pt(0) = pt(1)
pt(1) = pt(2)
pt(2) = pt(3)
pt(3).setxy(e.X, e.Y)
Dim no_of_interpolated_points
As Integer
= CInt(Math.Sqrt((Math.Pow(pt(2).x -
pt(1).x, 2) + Math.Pow(pt(2).y - pt(1).y, 2))))
BSPLINE(pt(0), pt(1), pt(2), pt(3), no_of_interpolated_points)
Dim i As
Integer
For i = 0 To
no_of_interpolated_points - 1
plus_draw(CInt(spline_out_x(i)),
CInt(spline_out_y(i)), 2, Color.Blue)
Next
i
Else
pt(Movement_Click).setxy(e.X, e.Y)
End If
Movement_Click = Movement_Click + 1
plus_draw(e.X, e.Y, 1, Color.Red)
End
Sub 'Form_MouseUp