Ellipses and Circles

An ellipse is a closed continuous line whose points are positioned so that two points exactly opposite each other have the exact same distant from a central point. It can be illustrated as follows:

Because an ellipse can fit in a rectangle, in GDI+ programming, an ellipse is defined with regards to a rectangle it would fit in. To draw an ellipse, you can use the Graphics.DrawEllipse() method that comes in four versions whose syntaxes are:

public void DrawEllipse(Pen pen, Rectangle rect);
public void DrawEllipse(Pen pen, RectangleF rect);
public void DrawEllipse(Pen pen, int x, int y, int width, int height);
public void DrawEllipse(Pen pen, float x, float y, float width, float height);

The arguments of this function play the same roll as those of the Graphics.DrawRectangle() method:

Here is an example:

private void button1_Click(object sender, System.EventArgs e)
{
	Graphics graph = this.CreateGraphics();

	Pen penCurrent = new Pen(Color.Red);
	graph.DrawEllipse(penCurrent, new Rectangle(20, 20, 226, 144));
}

Pies

A pie is a fraction of an ellipse delimited by two lines that span from the center of the ellipse to one side each. It can be illustrated as follows:

Like an ellipse (and like an arc), a pie is meant to fit in a rectangle. Based on this, a pie is delimited by a rectangular shaped that defines its location and the dimensions it would fit in.

To draw a pie, you can use the Graphics.DrawPie() method that comes in various versions as follows:

public void DrawPie(Pen pen,
                    Rectangle rect,
                    float startAngle,
                    float sweepAngle);
public void DrawPie(Pen pen,
                    RectangleF rect,
                    float startAngle,
                    float sweepAngle);
public void DrawPie(Pen pen,
                    int x,
                    int y,
                    int width,
                    int height,
                    int startAngle,
                    int sweepAngle);
public void DrawPie(Pen pen,
                    float x,
                    float y,
                    float width,
                    float height,
                    float startAngle,
                    float sweepAngle);

The first two versions allow you to specify a rectangle that would enclose the pie. The other two versions allow you to specify the location (with x and y) and dimensions of the pie. Besides the borders of the rectangle in which the pie would fit, a pie must specify its starting angle, startAngle, measured clockwise from the x-axis its starting point. A pie must also determine its sweep angle measured clockwise from the startAngle parameter to the end of the pie.

Here is an example: