フロントエンドアルゴリズムにおけるテキスト回避に関連する問題 (詳細なチュートリアル)

[
 {
 "name": "海门",//要显示的文字
 "lng": 121.15,
 "lat": 31.89,
 "count": 7,
 "pixel": { //像素坐标
  "x": 968,
  "y": 736
 }
 },
 {
 "name": "鄂尔多斯",
 "lng": 109.781327,
 "lat": 39.608266,
 "count": 5,
 "pixel": {
  "x": 659,
  "y": 478
 }
 },
...
]

let ctx = this.container.getContext('2d'); // canvas 上下文
let width= ctx.measureText(name).width;

let fontSize = parseInt(ctx.font);
let height = fontSize * 1.1;

_getLeftAnchor() {
  let x = this.center.x - this.radius - this.textReact.width,
    y = this.center.y - this.textReact.height / 2,
    diam = this.radius * 2,
    maxH = diam > this.textReact.height ? diam : this.textReact.height; //矩形的高度
  return {
    x,
    y,
    minX: x,
    maxX: this.center.x + this.radius,
    minY: this.center.y - maxH / 2,
    maxY: this.center.y + maxH / 2
  };
}

/**
 * 判断分位是否相交
 * @param {*} target 
 */ 
isAnchorMeet(target) {
  let react = this.getCurrentRect(),
    targetReact = target.getCurrentRect();
  if ((react.minX < targetReact.maxX) && (targetReact.minX < react.maxX) &&
    (react.minY < targetReact.maxY) && (targetReact.minY < react.maxY)) {
    return true;
  }
  return false;
}

let labels = pixels.map((val) => {
  let radius = val.pixel.radius + this.style.normal.borderWidth; //圆点半径
  return new Label(val.pixel.x, val.pixel.y, radius, fontSize, byteWidth, val.name);
});

do {
  var meet = false; //本轮是否有相交
  for (let i = 0; i < labels.length; i++) {
    let temp = labels[i];
    for (let j = 0; j < labels.length; j++) {
      if (i != j && temp.show && temp.isAnchorMeet(labels[j])) {
        temp.next();
        meet = true;
        break;
      }
    }
  }
} while (meet);

labels.forEach(function (item) {
  if (item.show) { //是否显示
    let pixel = item.getCurrentRect();
    ctx.beginPath();
    ctx.fillText(item.text, pixel.x, pixel.y);
    ctx.fill();
  }
});