Draw a circle in a cavas html element using the arc method.
ctx.arc(canvas.width / 2, canvas.height / 2, 100, 0, Math.PI * 2, false); ctx.strokeStyle = "blue"; ctx.stroke();
The arc canvas API method takes five (or optionally 6) arguments.
arc( x, y, r, sAngle, eAngle )
x The x-coordinate of the center of the circle,
y The y-coordinate of the center of the circle,
r The radius of the circle,
sAngle The starting angle, in radians (0 is at the 3 o’clock position of the arc’s circle),
eAngle The ending angle.
Note that the start / end angle of the arc is expressed in radians. That is why the end angle is
2*PI is equivalent to 360 degrees.