Graphics.DrawCurve Method (Pen, Point(), Int32, Int32, Single)

 

Draws a cardinal spline through a specified array of Point structures using a specified tension.

Namespace:   System.Drawing
Assembly:  System.Drawing (in System.Drawing.dll)

Public Sub DrawCurve (
	pen As Pen,
	points As Point(),
	offset As Integer,
	numberOfSegments As Integer,
	tension As Single
)

Parameters

pen
Type: System.Drawing.Pen

Pen that determines the color, width, and style of the curve.

points
Type: System.Drawing.Point()

Array of Point structures that define the spline.

offset
Type: System.Int32

Offset from the first element in the array of the points parameter to the starting point in the curve.

numberOfSegments
Type: System.Int32

Number of segments after the starting point to include in the curve.

tension
Type: System.Single

Value greater than or equal to 0.0F that specifies the tension of the curve.

Exception Condition
ArgumentNullException

pen is null.

-or-

points is null.

This method draws a cardinal spline that passes through each point in the array.

The array of points must contain at least three Point structures for a curve to be drawn.

The value of the offset parameter specifies the number of elements to skip in the array. The first element after the skipped elements represents the starting point of the curve.

The value of the numberOfSegments parameter specifies the number of segments, after the starting point, to draw in the curve. The value of the numberOfSegments parameter must be at least 1. The value of the offset parameter plus the value of the numberOfSegments parameter must be less than the number of elements in the array of the points parameter.

The tension parameter determines the shape of the spline. If the value of the tension parameter is 0.0F, this method draws straight line segments to connect the points. Usually, the tension parameter is less than or equal to 1.0F. Values over 1.0F produce unusual results.

The following code example is designed for use with Windows Forms, and it requires PaintEventArgse, which is a parameter of the Paint event handler. The code performs the following actions:

  • Creates red and green pens.

  • Creates seven points to define a curve.

  • Draws six red straight lines between the seven points to form an incomplete polygon.

  • Defines the starting point offset and number of segments.

  • Defines the tension.

  • Draws an open green curve (starting at the third point) through the last five points.

The method sets the tension to 1.0.

Private Sub DrawCurvePointSegmentTension(ByVal e As PaintEventArgs)

    ' Create pens.
    Dim redPen As New Pen(Color.Red, 3)
    Dim greenPen As New Pen(Color.Green, 3)

    ' Create points that define curve.
    Dim point1 As New Point(50, 50)
    Dim point2 As New Point(100, 25)
    Dim point3 As New Point(200, 5)
    Dim point4 As New Point(250, 50)
    Dim point5 As New Point(300, 100)
    Dim point6 As New Point(350, 200)
    Dim point7 As New Point(250, 250)
    Dim curvePoints As Point() = {point1, point2, point3, point4, _
    point5, point6, point7}

    ' Draw lines between original points to screen.
    e.Graphics.DrawLines(redPen, curvePoints)

    ' Create offset, number of segments, and tension.
    Dim offset As Integer = 2
    Dim numSegments As Integer = 4
    Dim tension As Single = 1.0F

    ' Draw curve to screen.
    e.Graphics.DrawCurve(greenPen, curvePoints, offset, numSegments, _
    tension)
End Sub

.NET Framework
Available since 1.1
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