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使用html2canvas进行截图操作

在 Vue 中使用 ​​html2canvas​​ 将 HTML 元素（如包含贝塞尔曲线的 Canvas/SVG）转换为图片

下载html2canvas

npm install html2canvas

在页面中使用，要截取哪个div的内容，先给这个div加一个ref标识，如ref=“html_container”

主要用到的：

具体代码：

<template><div class="CanvasPage" ref="html_container"><!-- 未处理时的canvas画布数据 --><canvas :id="'canvas' + '002'" :style="`position: absolute; `"></canvas><!-- 使用赛贝尔曲线以及笔锋处理之后的画布数据 --><canvas:id="'canvas' + '001'"@pointerdown.stop="onPointerDown":style="`position: absolute; `"@touchstart="onTouchstart"></canvas><div class="CanvasPageSave"><el-button @click="toSave" type="primary">保存当前页面</el-button></div></div>
</template><script setup>
import { ref, reactive, onMounted } from "vue";
import { Bezier } from "bezier-js";
import html2canvas from 'html2canvas'
let html_container = ref(null);
let canvas, ctx;
let canvasCover, ctxCover;
const winH = window.innerHeight,winW = window.innerWidth;let isMove = false;
// canvas初始化
const initCanvas = () => {canvas = document.getElementById("canvas001");ctx = canvas.getContext("2d", {antialias: true, // 抗锯齿});canvas.width = winW; // canvas宽度canvas.height = winH; // canvas高度ctx.lineWidth = 2; // 画线默认宽度ctx.strokeStyle = "red"; // 设置颜色// 复制出来一份原始的canvas画线数据canvasCover = document.getElementById("canvas002");ctxCover = canvasCover.getContext("2d", {antialias: true, // 抗锯齿});canvasCover.width = winW; // canvas宽度canvasCover.height = winH; // canvas高度ctxCover.lineWidth = 2; // 画线默认宽度ctxCover.strokeStyle = "red"; // 设置颜色
};let startx = ref(0), //起始坐标starty = ref(0),pointerId = ref(null);let points = []; // 收集所有点的数据// pointerdown同时处理鼠标、触摸屏和触控笔。
const onPointerDown = (e) => {points = [];isMove = true;const { offsetX, offsetY } = e;pointerId = e.pointerId;startx.value = offsetX;starty.value = offsetY;canvas.addEventListener("pointermove", onDrawMove);canvas.addEventListener("pointerup", onDrawUp);
};/* 单个触摸事件 */
// 处理移动逻辑
const onDrawMove = (e) => {if (isMove) {const { offsetX, offsetY } = e;if (pointerId != e.pointerId) return;// 原始画线数据ctxCover.beginPath();ctxCover.lineWidth = 2; // 设置线条粗细ctxCover.moveTo(startx.value, starty.value);ctxCover.lineTo(offsetX, offsetY);ctxCover.stroke();ctxCover.closePath();startx.value = offsetX;starty.value = offsetY;points.push({x: offsetX,y: offsetY,});e.preventDefault();}
}
// 处理释放逻辑
const onDrawUp = (e) => {ctx.closePath();// 鼠标释放时处理线条，将处理过的数据显示，之前的数据清空drawSmoothLine();points = [];isMove = false;document.removeEventListener("pointermove", onDrawMove);document.removeEventListener("pointerup", onDrawUp);
}
// 优化线条
const drawSmoothLine = () => {isMove = false;if (points.length > 1) {let num1 = 200; // 补点数let num2 = 20; // 从后面开始变细的点数const startWidth = 2; // 设置线条粗细const endWidth = 0; // 最后变细的宽度ctxCover.clearRect(0, 0, canvasCover.width, canvasCover.height); // 清除原始数据// 在释放的时候使用贝塞尔曲线重新处理画出来的线ctx.lineWidth = startWidth;// 设置线条粗细// 使用赛贝尔曲线让线条更丝滑const bez = new Bezier(points);const pointOnCurve = bez.getLUT(num1); // 补点ctx.beginPath();ctx.moveTo(pointOnCurve[0].x, pointOnCurve[0].y);// 截取，从开始截取到需要变细的位置，正常画线pointOnCurve.slice(0, -num2).forEach((p) => ctx.lineTo(p.x, p.y)); ctx.stroke();// 笔锋，设置线从哪个位置开始，按一定比例变细pointOnCurve.slice(-num2).forEach((p, px) => {const lineWidth = startWidth + ((endWidth - startWidth) * px) / num2;ctx.lineWidth = lineWidth;ctx.lineTo(p.x, p.y);ctx.stroke();});ctx.lineWidth = startWidth;ctx.closePath();}
};const toSave = () => {// html2canvas截取工具，第一个参数是截取的元素这里使用的ref，第二个参数是相应的配置html2canvas(html_container.value, {background: 'transparent',useCORS: true}).then((canvas) => {const base64 = canvas.toDataURL().replace(/^data:image\/(png|jpg);base64,/, '');// console.log(`data:image/png;base64,${base64}`);// 可选：自动下载图片const link = document.createElement('a');link.download = 'bezier-curve.png';link.href = `data:image/png;base64,${base64}`;link.click();});
}
onMounted(() => {initCanvas();
});
</script><style scoped lang="scss">
.CanvasPage {width: 100%;height: 100%;background-color: #044444;position: relative;.CanvasPageSave {position: absolute;left: 0;top: 0;}
}
</style>