How to draw a curve in windows application using C#?

Question

? · Accepted Answer

You can use GDI+ to draw curves in .NET framework. GDI+ supports several types of curves: ellipses, arcs, cardinal splines, and Bézier splines.

------Bell shaped cardinal spline------
Point[] points = {
   new Point(0, 100),
   new Point(50, 80),
   new Point(100, 20),
   new Point(150, 80),
   new Point(200, 100)};

Pen pen = new Pen(Color.FromArgb(255, 0, 0, 255));
e.Graphics.DrawCurve(pen, points);


-----Closed Cardinal Spline-----
Point[] points = {
   new Point(60, 60),
   new Point(150, 80),
   new Point(200, 40),
   new Point(180, 120),
   new Point(120, 100),
   new Point(80, 160)};

Pen pen = new Pen(Color.FromArgb(255, 0, 0, 255));
e.Graphics.DrawClosedCurve(pen, points);

------Single Bézier Spline -----
Point p1 = new Point(10, 100);   // Start point
Point c1 = new Point(100, 10);   // First control point
Point c2 = new Point(150, 150);  // Second control point
Point p2 = new Point(200, 100);  // Endpoint

Pen pen = new Pen(Color.FromArgb(255, 0, 0, 255));
e.Graphics.DrawBezier(pen, p1, c1, c2, p2);

-------Sequence of Bézier Splines -------
Point[] p = {
   new Point(10, 100),   // start point of first spline
   new Point(75, 10),    // first control point of first spline
   new Point(80, 50),    // second control point of first spline

   new Point(100, 150),  // endpoint of first spline and 
                         // start point of second spline

   new Point(125, 80),   // first control point of second spline
   new Point(175, 200),  // second control point of second spline
   new Point(200, 80)};  // endpoint of second spline

Pen pen = new Pen(Color.Blue);
e.Graphics.DrawBeziers(pen, p);

Asher · Answer

Here is a quick example, play around with the code..

private void button3_Click(object sender, System.EventArgs e)
{
  using (Graphics grf = CreateGraphics())
  {
    grf.Clear(Color.White);
    // create points for the cardinal spline curve
    Point[] pts = new Point[]
      {
        new Point(10, 210),
        new Point(150, 300),
        new Point(300, 270),
        new Point(220, 220)
      };
    // Draw the same curve with different tension values
    grf.DrawCurve(Pens.Black, pts, 1.0f);
    grf.DrawCurve(Pens.Red, pts, 0.0f);
    grf.DrawCurve(Pens.Blue, pts, 2.0f);
  }
}

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