使用canvas 根据角度画圆弧

最近收到一个需求，根据角度在平面上画出对应的区域，实际就是 以固定的原点，根据起始角度和结束角度和半径，画出他的区域。

写了一小段，试试

export class Draw {
  constructor(domId) {
    let canvas = document.getElementById(domId);
    this.initLoad = false
    this.storeName = ""
    this.canvas = canvas;
    this.context = canvas.getContext('2d'); //创建在画布上绘图的环境
  }
  init(x,y,offset=0) {
    // 圆心坐标 x, y .  起始角度的偏差值 offset
    this.initLoad = true
    this.cx = x;
    this.cy = y;
    this.offset = offset
  }
  mousemoveInit(callback) {
    let _this = this
    this.canvas.addEventListener("mousemove", function __handler__(evt) {
      if (!_this.initLoad) return
        var x = evt.clientX;
        var y = evt.clientY;
        var rect = _this.canvas.getBoundingClientRect();  //返回元素的大小及其相对于视口的位置
        x -= rect.left;
        y -= rect.top;
        let xl = Math.abs(x-_this.cx) //取绝对值
        let yl = Math.abs(y-_this.cy)
        let hl = _this.findHypotenuse(xl,yl)  //根据直角边，求斜边的长度
        if (hl<200){
          let ang = _this.getAngle(xl,yl,x,y) // 获取点相对圆心的角度， 0 度在横轴x 上
          let offsetAng = _this.getOffsetAngle(ang)
          callback(x, y,offsetAng)
          // console.log(x, y,offsetAng); // (x, y) 就是鼠标在 canvas 单击时的坐标 ang 是角度
        }else{
          callback(0, 0,500)
        }
        
    });
  }
  
  getOffsetAngle(ang) {
    // 根据计算的标准角度 返回用户需要的偏差角度
    return ang>90?ang-this.offset:ang+270
  }
  getAngle(x, y,ox,oy) {
      // 根据直角边 求角度
      var radian = Math.atan(y / x);//弧度    (y / x)为直线的斜率
      var angle = Math.floor(180 / (Math.PI / radian));//弧度转角度
      if (x < 0) {//x小于0的时候加上180°，即实际角度
          angle = angle + 180;
      }
      if (ox>=this.cx && oy>= this.cy) {
        return angle;
      } else if (ox  <= this.cx && oy>= this.cy) {
        return 180-angle
      }else if (ox  <= this.cx && oy<= this.cy) {
        return 180+angle
      }else if (ox>=this.cx && oy<= this.cy) {
        return 360-angle
      }
  }
  findHypotenuse (base,perpendicular) {
    // 根据直角边 求斜边的长度
    const bSquare = base ** 2;
    const pSquare = perpendicular ** 2;
    const sum = bSquare + pSquare;
    const hypotenuse = Math.sqrt(sum);  //返回一个数的平方根
    return Math.floor(hypotenuse);
  }
  mathAngle(angle,r) {
    // 根据角度求 坐标
    let angObj = {
      x: '',
      y: ''
    }
    var angles = 0;
    var radian = 0;
    if (angle<=90) {
      angles = 90-angle
    }else if (angle>90 && angle <=180) {
      angles = angle-90
    }else if (angle>180 && angle <=270) {
      angles = 270- angle
    }else if (angle>270 && angle <=360) {
      angles = angle-270
    }
    radian = angles * Math.PI / 180
    let xlen = Math.floor(Math.sin(radian)*r)
    let ylen = Math.floor(Math.cos(radian)*r)
    
    if (angle<=90) {
      angObj.x = this.cx+xlen
      angObj.y = this.cy+ylen
    }else if (angle>90 && angle <=180) {
      angObj.x = this.cx-xlen
      angObj.y = this.cy+ylen
    }else if (angle>180 && angle <=270) {
      angObj.x = this.cx-xlen
      angObj.y = this.cy-ylen
    }else if (angle>270 && angle <=360) {
      angObj.x = this.cx+xlen
      angObj.y = this.cy-ylen
    }
    return angObj
  }
  clearRect () {
    // 清除画布
    this.context.clearRect(0,0,this.cx*2,this.cy*2);
  }
  lines (x1,y1,x2,y2,color,width=5) {
    // 画直线
    this.context.beginPath();
    this.context.lineWidth = width;
    this.context.moveTo(x1,y1);
    
    this.context.lineTo(x2,y2); 
    this.context.strokeStyle = color; 
    this.context.stroke();
  }


  pieChart(r,sAngle,eAngle,color,flag=true) {
    // 画扇形
    let startAngle = 2*sAngle/360
    let endAngle = 2*eAngle/360
    this.context.beginPath();
    this.context.lineWidth = 1;
    this.context.moveTo(this.cx,this.cy);
    this.context.strokeStyle = "white";
    this.context.fillStyle = color;
    this.context.arc(this.cx,this.cy,r,startAngle*Math.PI,endAngle*Math.PI);
    this.context.fill();
    this.context.closePath();
    this.context.stroke();
  }
  pieName(x,y,color,name) {
    //文字绘制到扇形旁边
    this.context.fillText(name,x,y);
  }
}



export class Angle extends Draw {
  correct (ang) {
    // 将传入的角度按照偏差值 进行纠正
    return ang+this.offset<=360?ang+this.offset:ang+this.offset-360
  }
  correctM (sAngle,eAngle) {
    // 取俩角度中间值
    if (sAngle > eAngle) {
      let ang = sAngle + 1/2*(360-sAngle+eAngle);
      return ang>360?ang-360:ang
    }
    return sAngle + 1/2*(eAngle-sAngle);
  }
  drawAir (r,sAngle,eAngle,color,name) {
    // 画分区的扇形
    sAngle = this.correct(sAngle)
    eAngle = this.correct(eAngle)
    this.pieChart(r,sAngle,eAngle,color,name)
    
  }
  drawName (r,sAngle,eAngle,color,name) {
    // 画分区的名字
    sAngle = this.correct(sAngle)
    eAngle = this.correct(eAngle)
    //计算文字要放的角度
    var txtAngle = this.correctM(sAngle,eAngle)
    this.context.textAlign = 'center';
    if(txtAngle>95 && txtAngle<260){
      this.context.textAlign = 'end';
    }
    if(txtAngle<85 && txtAngle>5){
      this.context.textAlign = 'left';
    }
    if(txtAngle<350 && txtAngle>275){
      this.context.textAlign = 'left';
    }
    
    var x,y;
    x=this.cx+Math.cos(txtAngle*Math.PI/180)*(r+20);
    y=this.cy+Math.sin(txtAngle*Math.PI/180)*(r+20);
    this.pieName(x,y,color,name)
    
  }
  drawMachine(r,angle,color) {
    // 画机器的位置
    this.lines(this.cx,this.cy,40,140,"#ff0")
  }
}

<template>
    <canvas id="can" width="600" height="600"></canvas>
</template>
<script>
import {onMounted} from 'vue'
import {Draw} from './draw.js'
export default {
  setup(){
    function pageLoad(){
      let draw = new Draw('can')
      draw.init(300,300)
      draw.airAngle(200,20,90,'#ff0',false)
      draw.airAngle(200,150,290,'#ff8',false)
      draw.mousemoveInit((x, y,ang)=>{
        console.log(x, y,ang)
      })
    }
    onMounted(() =>{
      pageLoad()
    })
  }
  
}
</script>

得到了这样的效果

 鼠标滑到 对应的区域，将返回该点的坐标 和角度