[orx-shapes] Add Circle.contour(segments), Ellipse.contour(segments)

orx-shapes/src/commonMain/kotlin/Circle.kt

@@ -0,0 +1,36 @@
+import org.openrndr.math.Polar
+import org.openrndr.math.Vector2
+import org.openrndr.math.transforms.buildTransform
+import org.openrndr.shape.Circle
+import org.openrndr.shape.Ellipse
+import org.openrndr.shape.ShapeContour
+import org.openrndr.shape.contour as buildContour
+
+/**
+ * Convert [Circle] to [ShapeContour] with a number of segments equal to [segments]
+ * @param segments the number of segments, at least 4
+ */
+fun Circle.contour(segments: Int): ShapeContour {
+    return buildContour {
+        val p = Polar(0.0, radius)
+        moveTo(center + p.cartesian)
+        for (i in 1 until segments+1) {
+            val p = Polar(i * 360.0/segments, radius).cartesian + center
+            arcTo(radius, radius, 360.0/segments, false, true, p.x, p.y)
+        }
+        close()
+    }
+}
+
+/**
+ * Convert [Ellipse] to [ShapeContour] with a number of segments equal to [segments]
+ * @param segments the number of segments, at least 4
+ */
+fun Ellipse.contour(segments: Int): ShapeContour {
+    return Circle(Vector2.ZERO, xRadius).contour(segments).transform(
+        buildTransform {
+            translate(center)
+            scale(1.0, yRadius/xRadius)
+        }
+    )
+}