fonteditor-core/lib/math/bezierCubic2Q2.js

fonts (ttf, woff, woff2, eot, svg, otf) parse, write, transform, glyph adjust.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = bezierCubic2Q2;
/**
 * @file 三次贝塞尔转二次贝塞尔
 * @author mengke01(kekee000@gmail.com)
 *
 * references:
 * https://github.com/search?utf8=%E2%9C%93&q=svg2ttf
 * http://www.caffeineowl.com/graphics/2d/vectorial/cubic2quad01.html
 *
 */

function toQuad(p1, c1, c2, p2) {
  // Quad control point is (3*c2 - p2 + 3*c1 - p1)/4
  var x = (3 * c2.x - p2.x + 3 * c1.x - p1.x) / 4;
  var y = (3 * c2.y - p2.y + 3 * c1.y - p1.y) / 4;
  return [p1, {
    x: x,
    y: y
  }, p2];
}

/**
 * 三次贝塞尔转二次贝塞尔
 *
 * @param {Object} p1 开始点
 * @param {Object} c1 控制点1
 * @param {Object} c2 控制点2
 * @param {Object} p2 结束点
 * @return {Array} 二次贝塞尔控制点
 */
function bezierCubic2Q2(p1, c1, c2, p2) {
  // 判断极端情况，控制点和起止点一样
  if (p1.x === c1.x && p1.y === c1.y && c2.x === p2.x && c2.y === p2.y) {
    return [[p1, {
      x: (p1.x + p2.x) / 2,
      y: (p1.y + p2.y) / 2
    }, p2]];
  }
  var mx = p2.x - 3 * c2.x + 3 * c1.x - p1.x;
  var my = p2.y - 3 * c2.y + 3 * c1.y - p1.y;

  // control points near
  if (mx * mx + my * my <= 4) {
    return [toQuad(p1, c1, c2, p2)];
  }

  // Split to 2 qubic beziers by midpoints
  // (p2 + 3*c2 + 3*c1 + p1)/8
  var mp = {
    x: (p2.x + 3 * c2.x + 3 * c1.x + p1.x) / 8,
    y: (p2.y + 3 * c2.y + 3 * c1.y + p1.y) / 8
  };
  return [toQuad(p1, {
    x: (p1.x + c1.x) / 2,
    y: (p1.y + c1.y) / 2
  }, {
    x: (p1.x + 2 * c1.x + c2.x) / 4,
    y: (p1.y + 2 * c1.y + c2.y) / 4
  }, mp), toQuad(mp, {
    x: (p2.x + c1.x + 2 * c2.x) / 4,
    y: (p2.y + c1.y + 2 * c2.y) / 4
  }, {
    x: (p2.x + c2.x) / 2,
    y: (p2.y + c2.y) / 2
  }, p2)];
}