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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 void DrawCurve(
	Pen pen,
	Point[] points,
	int offset,
	int numberOfSegments,
	float tension
)

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.

ExceptionCondition
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 PaintEventArgs e, 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 void DrawCurvePointSegmentTension(PaintEventArgs e)
{

    // Create pens.
    Pen redPen = new Pen(Color.Red, 3);
    Pen greenPen = new Pen(Color.Green, 3);

    // Create points that define curve.
    Point point1 = new Point(50, 50);
    Point point2 = new Point(100, 25);
    Point point3 = new Point(200, 5);
    Point point4 = new Point(250, 50);
    Point point5 = new Point(300, 100);
    Point point6 = new Point(350, 200);
    Point point7 = new Point(250, 250);
    Point[] curvePoints = {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. 
    int offset = 2;
    int numSegments = 4;
    float tension = 1.0F;

    // Draw curve to screen.
    e.Graphics.DrawCurve(greenPen, curvePoints, offset, numSegments, tension);
}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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