How do I draw an arc that goes from 0 degrees to 180, and his perimiter is 20mm?

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How do I draw an arc that goes from 0 degrees to 180, and his perimiter is 20mm?

The picture with an explanation[^]

What I have tried:

C#

Graphics g = Graphics.FromImage(bmp);
g.PageUnit = GraphicsUnit.Millimeter;
Rectangle r = new Rectangle(0, 0, (int)(Math.Round((40 / 25.4) / (float)Math.PI * g.DpiX) * 2), (int)(Math.Round((40 / 25.4) / (float)Math.PI * g.DpiY) * 2));
g.DrawArc(Pens.Black, r, 0, 180);

This is what I tried so far. I've came to this conclusion :

C#

g.DrawLine(Pens.Black, 1, 1, 1, (float)Math.Round((2 / 25.4) * g.DpiY));

This code draws a line that is 2mm long. But the first part of code which is supposed to be working good isn't working for some reason and its displaying a semiarc bigger than its supposed to be.

Posted 8-Dec-17 7:03am

Member 12137971

Updated 11-Dec-17 3:23am

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alywaly · Answer 1 · 2017-12-11T03:23:00

I would use the graphics DrawArc method and call this from overridden OnPaint(PaintEventArgs e)

private void MyDrawArc(PaintEventArgs e)
{
// Create pen.d
Pen pen = new Pen(Color.Black, 22);

// coordinates
int x = 100;
int y = 100;
int width = 200;
int height = 200;

// start and sweep angles
int startAngle = 0;
int sweepAngle = -180;

// Draw the arc to the screen.
e.Graphics.PageUnit = GraphicsUnit.Millimeter;
e.Graphics.DrawArc(pen, x, y, width, height, startAngle, sweepAngle);
}