canvas给图片画框框

<template>
  <div class="item-img">
    <canvas id="myCanvas" width="1280" height="650">
      Your browser does not support the HTML5 canvas tag.
    </canvas>
  </div>
</template>
<script>
export default {
    
  data() {
    
    return {
    };
  },
//src为图片路径，gtcoord为gt标注数据：[[x,x,x,x],[x,x,x,x]......],dt同理
  props: ["src", "gtcoord", "dtcoord"],
  mounted() {
    
    this.imgURL = this.src;
    this.queryCanvasInfo();
  },
  methods: {
    
    //获取canvasdom节点
    queryCanvasInfo() {
    
      (this.c = document.getElementById("myCanvas")),
        (this.ctx = this.c.getContext("2d"));
      this.img = new Image();
      this.img.src = this.imgURL;
      this.createCanvasImg();
    },
    //创建图片画布
    createCanvasImg() {
    
    // this.imgX = this.c.width / 2; //拖拽的X轴值
    // this.imgY = this.c.height / 2; //拖拽的Y轴值
      let img = this.img;
      img.src = this.imgURL; //更换图片
      img.onload = () => {
    
        //图片加载时
        this.ctx.clearRect(0, 0, this.c.width, this.c.height); //清空这个范围的画布
        let a = img.width / img.height; //计算原始图片的宽高比例
        console.log(img.width, img.height, 999);
        if (img.width > img.height) {
    
          //当图片宽度大于高度则写死宽度按高度调整比例
          this.maxW = this.c.width; //最大宽度要等于画布的宽度
          this.maxH = this.maxW / a;
        } else {
    
          //相反
          (this.maxH = this.c.height), (this.maxW = this.maxH * a);
        }
         this.times = this.img.width / this.maxW; //计算原图与canvas的比例
        this.canvasInfo(); //重新绘制图片
      };
    },
    //绘制图片
    canvasInfo() {
    
      let w = this.maxW, //计算缩放的宽度
        h = this.maxH; //计算缩放的高度
      this.ctx.drawImage(
        this.img, //图片实例
        0,
        0, //x轴y轴的边距
        w,
        h //图片的宽高
      );
      this.canvasRect( this.dtcoord,"dt");
      this.canvasRect( this.gtcoord,"gt");
    },
    //标注框绘制
    canvasRect(list,txt) {
    
      list.forEach((item) => {
    
        if (!item) return;
        let ary = item,
          x = Number(ary[0]) / this.times,
          y = Number(ary[1]) / this.times,
          w = Number(ary[2]) / this.times,
          h = Number(ary[3])/ this.times;   
        this.ctx.lineWidth = "1"; //框的粗细
        if(txt=="gt"){
    
             this.ctx.strokeStyle = "yellow"; //gt选中的标注框为红色
        }else{
    
            this.ctx.strokeStyle = "red"; //dt选中的标注框为红色
        }  
       //开始绘制
        this.ctx.strokeRect(x, y, w, h);
      });
    },
  },
};
</script>
<style lang="less" scoped>
.item-img {
    
 text-align: center;
}
</style>