Java Utililty Methods Geometry Circle

Polygon circle2poly(float x, float y, float radius)
circlepoly

float dphi = 2.0f / radius;
int nangles = (int) ((2.0f * (float) Math.PI) / dphi);
int[] xpts = new int[nangles];
int[] ypts = new int[nangles];
for (int i = 0; i < nangles; i++) {
 float phi = dphi * i;
 xpts[i] = (int) (radius * (float) Math.cos(phi) + x);
 ypts[i] = (int) (radius * (float) Math.sin(phi) + y);
...

Shape circleArrow(double size)
circle Arrow

Ellipse2D circle = new Ellipse2D.Double(-size, -size / 2.0, size, size);
return circle;

Point2D circleCentre(double x1, double y1, double x2, double y2, double x3, double y3)
circle Centre

x2 -= x1;
x3 -= x1;
y2 -= y1;
y3 -= y1;
final double sq2 = (x2 * x2 + y2 * y2);
final double sq3 = (x3 * x3 + y3 * y3);
final double x = (y2 * sq3 - y3 * sq2) / (y2 * x3 - y3 * x2);
return new Point2D.Double(x1 + 0.5 * x, y1 + 0.5 * (sq2 - x * x2) / y2);
...

Point2D.Double circleCentre(double x1, double y1, double x2, double y2, double x3, double y3)
Returns a circle passing by the 3 given points.

x2 -= x1;
x3 -= x1;
y2 -= y1;
y3 -= y1;
final double sq2 = (x2 * x2 + y2 * y2);
final double sq3 = (x3 * x3 + y3 * y3);
final double x = (y2 * sq3 - y3 * sq2) / (y2 * x3 - y3 * x2);
return new Point2D.Double(x1 + 0.5 * x, y1 + 0.5 * (sq2 - x * x2) / y2);
...

Polygon pCircle(int x, int y, int r)
returns a polygon approximation to a circle of radius r at location x, y

Polygon p = new Polygon();
for (int k = -r; k < r; k += 1) {
 int m = x + k;
 int n = (int) Math.sqrt(r * r - k * k);
 p.addPoint(m, y + n);
for (int k = r; k > -r; k -= 1) {
 int m = x + k;
...