Created
June 30, 2018 21:32
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Convert a Circle shape to a set of Bezier curves (SVG Path string) using Javascript
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export default function circleToBezier(cx, cy, r) { | |
// Inspired by https://codereview.stackexchange.com/questions/141491/calculating-a-circle-with-bezier-curves | |
function Coord(x, y) { | |
var self = this; | |
this.x = parseFloat(x); | |
this.y = parseFloat(y); | |
this.offset = function(offsetX, offsetY) { | |
self.x += offsetX; | |
self.y += offsetY; | |
} | |
} | |
Coord.prototype.toString = function () { | |
return `${this.x} ${this.y}` | |
} | |
function BezierCurve(x, y, c1, c2) { | |
var self = this; | |
this.x = x; | |
this.y = y; | |
this.c1 = c1; | |
this.c2 = c2; | |
this.offset = function(offsetX, offsetY) { | |
self.x += offsetX; | |
self.y += offsetY; | |
self.c1.offset(offsetX, offsetY); | |
self.c2.offset(offsetX, offsetY); | |
} | |
} | |
BezierCurve.prototype.toString = function () { | |
return `${this.c1.toString()} ${this.c2.toString()} ${this.x} ${this.y}` | |
} | |
var BEZIER_CONTROL_POINT = 0.552284749831; | |
var twoR = r * 2; | |
var offsetX = cx - r; | |
var offsetY = cy - r; | |
var controlPointOffset = r * BEZIER_CONTROL_POINT; | |
// from Middle Left | |
var firstMove = new Coord(0, r); | |
// curve to Top Middle | |
var curve1 = new BezierCurve(r, 0, | |
new Coord(0, r - controlPointOffset), | |
new Coord(r - controlPointOffset, 0)); | |
// curve to Middle Right | |
var curve2 = new BezierCurve(twoR, r, | |
new Coord(r + controlPointOffset, 0), | |
new Coord(twoR, r - controlPointOffset)); | |
// curve to Bottom Middle | |
var curve3 = new BezierCurve(r, twoR, | |
new Coord(twoR, r + controlPointOffset), | |
new Coord(r + controlPointOffset, twoR)); | |
// curve back to Middle Left | |
var curve4 = new BezierCurve(0, r, | |
new Coord(r - controlPointOffset, twoR), | |
new Coord(0, r + controlPointOffset)); | |
if (offsetX > 0) { | |
firstMove.offset(offsetX, offsetY); | |
curve1.offset(offsetX, offsetY); | |
curve2.offset(offsetX, offsetY); | |
curve3.offset(offsetX, offsetY); | |
curve4.offset(offsetX, offsetY); | |
} | |
let output = ''; | |
output += (`M ${firstMove.toString()}`); | |
output += (`C ${curve1.toString()}`); | |
output += (`C ${curve2.toString()}`); | |
output += (`C ${curve3.toString()}`); | |
output += (`C ${curve4.toString()}`); | |
output += ("Z"); | |
return output; | |
} |
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