vue3+canvas 绘制坐标

在Vue 3中，你可以创建一个自定义组件来使用Canvas绘制坐标系。以下是一个简单的例子：

<template>
  <canvas ref="canvas" @click="drawCoordinate($event)"></canvas>
</template>
 
<script setup>
import { ref, onMounted } from 'vue';
 
const canvas = ref(null);
const drawCoordinate = (event) => {
  const ctx = canvas.value.getContext('2d');
  const rect = canvas.value.getBoundingClientRect();
 
  ctx.clearRect(0, 0, canvas.value.width, canvas.value.height); // Clear canvas
  ctx.beginPath();
  ctx.strokeStyle = '#000';
  ctx.lineWidth = 2;
  ctx.setLineDash([5, 15]);
 
  // Draw x axis
  ctx.moveTo(rect.left, event.clientY - rect.top);
  ctx.lineTo(rect.left + canvas.value.width, event.clientY - rect.top);
 
  // Draw y axis
  ctx.moveTo(event.clientX - rect.left, rect.top);
  ctx.lineTo(event.clientX - rect.left, rect.top + canvas.value.height);
 
  ctx.stroke();
};
 
onMounted(() => {
  canvas.value.width = canvas.value.offsetWidth;
  canvas.value.height = canvas.value.offsetHeight;
});
</script>
 
<style>
canvas {
  border: 1px solid #000;
  cursor: crosshair;
}
</style>

这个组件在被挂载后会设置canvas的宽度和高度，然后在canvas上绘制坐标系。用户点击canvas时，会绘制出点击位置的X轴和Y轴。使用setLineDash方法设置虚线样式。