addBezier method

dynamic addBezier(dynamic x0, dynamic y0, dynamic x1, dynamic y1, dynamic x2, dynamic y2, dynamic x, dynamic y,)

Add a Bézier curve to the bounding box. This extends the bounding box to include the entire Bézier. @param {number} x0 - The starting X coordinate. @param {number} y0 - The starting Y coordinate. @param {number} x1 - The X coordinate of the first control point. @param {number} y1 - The Y coordinate of the first control point. @param {number} x2 - The X coordinate of the second control point. @param {number} y2 - The Y coordinate of the second control point. @param {number} x - The ending X coordinate. @param {number} y - The ending Y coordinate.

Implementation

addBezier(x0, y0, x1, y1, x2, y2, x, y) {
    // This code is based on http://nishiohirokazu.blogspot.com/2009/06/how-to-calculate-bezier-curves-bounding.html
    // and https://github.com/icons8/svg-path-bounding-box

    var p0 = [x0, y0];
    var p1 = [x1, y1];
    var p2 = [x2, y2];
    var p3 = [x, y];

    this.addPoint(x0, y0);
    this.addPoint(x, y);

    for (var i = 0; i <= 1; i++) {
        var b = 6 * p0[i] - 12 * p1[i] + 6 * p2[i];
        var a = -3 * p0[i] + 9 * p1[i] - 9 * p2[i] + 3 * p3[i];
        var c = 3 * p1[i] - 3 * p0[i];

        if (a == 0) {
            if (b == 0) continue;
            var t = -c / b;
            if (0 < t && t < 1) {
                if (i == 0) this.addX(derive(p0[i], p1[i], p2[i], p3[i], t));
                if (i == 1) this.addY(derive(p0[i], p1[i], p2[i], p3[i], t));
            }
            continue;
        }

        var b2ac = Math.pow(b, 2) - 4 * c * a;
        if (b2ac < 0) continue;
        var t1 = (-b + Math.sqrt(b2ac)) / (2 * a);
        if (0 < t1 && t1 < 1) {
            if (i == 0) this.addX(derive(p0[i], p1[i], p2[i], p3[i], t1));
            if (i == 1) this.addY(derive(p0[i], p1[i], p2[i], p3[i], t1));
        }
        var t2 = (-b - Math.sqrt(b2ac)) / (2 * a);
        if (0 < t2 && t2 < 1) {
            if (i == 0) this.addX(derive(p0[i], p1[i], p2[i], p3[i], t2));
            if (i == 1) this.addY(derive(p0[i], p1[i], p2[i], p3[i], t2));
        }
    }
}