vue实现canvas画很多条线，点击那条线就删除那条线需求。

公司最近提了个新需求，就是要在canvas画板上要画许多条线，点击那条线就删除那条线的功能，刚开始我用的原生canvas，很麻烦并不容易实现。于是改变思路，用到了'KonvaJS'

1、KonvaJS 是一个功能强大的Html5 Canvas库。

文档：https://konvajs.org/docs/vue/index.html

npm install vue-konva@2 konva --save

2、引用

在main.js中

import VueKonva from 'vue-konva';

Vue.use(VueKonva);

 3、使用

<div id="box_img">
 <v-stage
   class="palette"
   id="canvas"
   ref="canvas"
   :config="{ width: chartWidth, height: chartHeight }"  //动态获取的canvas宽高
   @mousedown="stageMousedown"
   @mousemove="stageMousemove"
   @mouseup="stageMouseup"
                      >
  <v-layer>
  <v-line
    v-for="(item, index) in lines"
    :config="item"
    @click="lineDel(index)"
   />
   </v-layer>
  </v-stage>
 <div>
　<div @click='ftchEraser'>橡皮</div>

　　　//获取画布的宽高

      let box = document.getElementById("box_img");

      let width = box.offsetWidth;

      let height = box.offsetHeight;

      this.chartWidth = box.offsetWidth;

      this.chartHeight = box.offsetHeight;

4、js部分

　ftchEraser() {

     this.isEraser = !this.isEraser;

  },

stageMousedown() {this.isPaint = true;
        const stage = this.$refs.canvas.getStage();
        const pos = stage.getPointerPosition();
        this.lines.push({   //存到一个空数组中把数据
          stroke: "red",
          strokeWidth: 2,  //这块设置线条颜色、粗细
          points: [pos.x, pos.y],
        });
    },
    stageMousemove() {
      if (!this.isPaint) {
        return;
      }
      const stage = this.$refs.canvas.getStage();
      const pos = stage.getPointerPosition();
      const lastLine =
        this.lines[this.lines.length === 1 ? 0 : this.lines.length - 1];
      const newPoints = lastLine.points.concat([pos.x, pos.y]);
      lastLine.points = newPoints;
    },
    stageMouseup() {
      this.isPaint = false;
      this.lines = this.lines.filter((item) => item.points.length !== 2);
    },
    lineDel(index) {
      if (this.isEraser) {
        this.lines.splice(index, 1); //这块点击线条删除部分
      }
    },