碰撞检测

/**

• 简单碰撞冲突
• @remarks
• 类似聚合，距离判断，速度快
• /
  export class SimpleCollision {
  /**
  • 检测距离
  • @remarks
  • 单位 pixel
  • /
    public distance: number = 50;
    /**
  • 冲突检测
  • @param {Feature[]} features - 准备绘制标注的要素集合
  • @param {Field} field - 标注字段
  • @param {SimpleTextSymbol} symbol - 标注文本符号
  • @param {CanvasRenderingContext2D} ctx - 绘图上下文
  • @param {Projection} projection - 坐标投影转换
  • @return {Feature[]} 返回可绘制标注的要素集合
  • /
    test(features: Feature[], field: Field, symbol: SimpleTextSymbol, ctx: CanvasRenderingContext2D, projection: Projection = new WebMercator()): Feature[] {
    //根据距离聚合
    return features.reduce( (acc, cur) => {

      const item: any = acc.find((item: any) => {
          const distance = cur.geometry.distance(item.geometry, CoordinateType.Screen, ctx, projection);
          return distance <= this.distance;
      });
      if (!item) acc.push(cur);
      return acc;
    

    }, []); // [feature]
    }
    }

/**

• 叠盖碰撞冲突
• @remarks
• 试算标注宽高，并和已通过检测的标注，进行边界的交叉判断，速度慢
• /
  export class CoverCollision {
  /**
  • 已通过检测的标注的边界集合
  • /
    private _bounds: Bound[] = [];
    /**
  • 判断边界碰撞时的buffer
  • @remarks
  • buffer越小，标注越密，单位：pixel
  • /
    public buffer: number = 10;
    /**
  • 冲突检测
  • @param {Feature[]} features - 准备绘制标注的要素集合
  • @param {Field} field - 标注字段
  • @param {SimpleTextSymbol} symbol - 标注文本符号
  • @param {CanvasRenderingContext2D} ctx - 绘图上下文
  • @param {Projection} projection - 坐标投影转换
  • @return {Feature[]} 返回可绘制标注的要素集合
  • /
    test(features: Feature[], field: Field, symbol: SimpleTextSymbol, ctx: CanvasRenderingContext2D, projection: Projection = new WebMercator()): Feature[] {
    if (!field || !symbol) return [];
    this._bounds = [];
    //根据标注宽高的量算，得到标注的size，并和已通过检测的标注，进行边界的交叉判断，来决定是否可绘制该要素的标注
    return features.reduce( (acc, cur) => {

      const bound = cur.geometry.measure(cur.properties[field.name], ctx, projection, symbol);
      if (bound) {
          bound.buffer(this.buffer);
          const item = this._bounds.find( item => item.intersect(bound) );
          if (!item) {
              acc.push(cur);
              this._bounds.push(bound);
          }
      }
      return acc;
    

    }, []); // [feature]
    }
    }