methods show thistouched = false; thisvisible = true; let that = this; setTimeoutfunction let canvas = that$refssignatureBoard; thatboundInfo = canvasg

在Vue3中，可以使用Composition API来重写上述代码。首先，需要在组件中引入ref和onMounted方法。

import { ref, onMounted } from 'vue';

export default {
  setup() {
    const touched = ref(false);
    const visible = ref(true);
    let boundInfo = null;
    let canvasContext = null;
    const points = ref([]);

    const show = () => {
      touched.value = false;
      visible.value = true;

      setTimeout(() => {
        const canvas = canvasRef.value;
        boundInfo = canvas.getBoundingClientRect();
        canvas.height = canvas.offsetHeight;
        canvas.width = canvas.offsetWidth;
        canvasContext = canvas.getContext('2d');
        canvasContext.lineWidth = 4;
        canvasContext.lineJoin = 'round';
        canvasContext.lineCap = 'round';
        canvasContext.strokeStyle = '#ff461f';
        canvasContext.fillStyle = 'rgba(255, 255, 255, 0)';
        canvasContext.fillRect(0, 0, boundInfo.width, boundInfo.height);
        points.value = [];
      }, 100);
    };

    onMounted(() => {
      show();
    });

    return {
      touched,
      visible,
      boundInfo,
      canvasContext,
      points,
      show
    };
  }
};

在以上代码中，我们使用了ref来声明touched、visible和points等响应式数据，并通过onMounted来在组件挂载后执行show方法。在show方法中，我们使用了canvasRef来获取canvas元素的引用，并使用canvasContext来绘制画布。

注意，在Vue3中，我们使用ref来替代Vue2中的data属性，使用onMounted来替代Vue2中的mounted钩子函数