MyPrint打印设计器（十）svg篇-多边形
svg-多边形
介绍一款强大的svg操作库，能够通过简单的代码，实现svg绘制与操纵，实现拖拽等功能
本文将通过一个简单的示例，介绍如何在SVG中绘制一条可拖拽的多边形
代码仓库
在线体验
代码仓库：github
代码仓库：gitee
实战项目：MyPrint
操作简单，组件丰富的一站式打印解决方案打印设计器
体验地址：前往
代码仓库：github
代码仓库：gitee
demo 效果
实战项目效果
正文
基础HTML结构
首先，我们需要在HTML中设置基本的SVG元素，以便绘制图形。
<html lang="en">
<head><meta charset="UTF-8"><title>MyPrint | 打印设计 | SVG | 多边形</title><script src="https://cdn.jsdelivr.net/npm/d3@7"></script><style>body {width: 100vw;height: 100vh;margin: 0;display: flex;justify-content: center;align-items: center;}.chart {width: 100%;height: 100%;overflow: visible;}.chart_wrapper {width: 700px;height: 700px;box-shadow: 2px 2px 10px rgba(10, 10, 10, 0.1);border-radius: 10px;}</style>
</head>
<body>
<div class="chart_wrapper"><svg id="chartRef" class="chart"><path class="u-path"/><line class="u-line"/><line class="u-line"/></svg>
</div>
</body>
</html>
绘制 SVG 矩形
接下来，我们使用 D3.js 创建一个简单的矩形，并通过 JavaScript 函数 freshSvg 进行渲染。代码如下：
const chartElement = document.getElementById('chartRef');function freshSvg() {const x0 = 100, y0 = 200,x1 = 500, y1 = 100,x2 = 500, y2 = 500,x3 = 200, y3 = 500;const points = [[x0, y0], [x1, y1], [x2, y2], [x3, y3]];const draw = () => {const path = d3.path();path.moveTo(...points[0]);path.lineTo(...points[1]);path.lineTo(...points[2]);path.lineTo(...points[3]);path.closePath();return path;};draggable(chartElement, points, [], [], draw, {fill: 'orange'});
}
freshSvg();
这里，我们定义了矩形的四个顶点，并通过 d3.path() 方法绘制了这个矩形。
实现拖拽功能
为了让用户可以拖动矩形的顶点，我们使用 D3.js 的 drag 功能，并结合 draggable 函数实现这一功能：
function draggable(chart, points, labels, lines, draw, options) {update(chart, points, labels, lines, draw, options);const dist = (p, m) => Math.sqrt((p[0] - m[0]) ** 2 + (p[1] - m[1]) ** 2);let subject, dx, dy;function dragSubject(event) {const p = d3.pointer(event.sourceEvent, chart);subject = d3.least(points, (a, b) => dist(p, a) - dist(p, b));return subject && dist(p, subject) <= 48 ? subject : null;}d3.select(chart).on("mousemove", event => dragSubject({sourceEvent: event})).call(d3.drag().subject(dragSubject).on("start", event => {if (subject) {dx = subject[0] - event.x;dy = subject[1] - event.y;}}).on("drag", event => {if (subject) {subject[0] = event.x + dx;subject[1] = event.y + dy;}}).on("end", () => {d3.select(chart).style("cursor", "grab");}).on("start.render drag.render end.render", () =>update(chart, points, labels, lines, draw, options)));
}
在 draggable 函数中，我们为每个顶点设置了拖拽行为，当用户拖动顶点时，矩形会相应地更新其形状。
完整实现
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>MyPrint|打印设计|SVG|矩形</title><script src="https://cdn.jsdelivr.net/npm/d3@7"></script><script src="./d3-utils.js"></script><style>body {width: 100vw;height: 100vh;margin: 0;display: flex;justify-content: center;align-items: center;}.chart {width: 100%;height: 100%;overflow: visible;}.chart_wrapper {width: 700px;height: 700px;box-shadow: 2px 2px 10px rgba(10, 10, 10, 0.1);border-radius: 10px;}</style>
</head><body>
<div class="chart_wrapper"><svg id="chartRef" class="chart"><path class="u-path" :d="path"/><line class="u-line"/><line class="u-line"/></svg>
</div>
</body><script>const chartElement = document.getElementById('chartRef')const path = d3.path();function freshSvg() {const x0 = 100,y0 = 200,x1 = 500,y1 = 100,x2 = 500,y2 = 500,x3 = 200,y3 = 500;const path = d3.path();path.moveTo(x0, y0);path.moveTo(x1, y1);path.moveTo(y2, y2);path.moveTo(x3, y3);/*** 控制点*/const points = [[x0, y0], [x1, y1], [x2, y2], [x3, y3]],// labels = ["Start", "Control", "End", '123'],labels = [],// lines = [[points[0], points[1]], [points[1], points[2]]],lines = [],draw = () => {const path = d3.path();path.moveTo(...points[0]);path.lineTo(...points[1]);path.lineTo(...points[2]);path.lineTo(...points[3]);// path.moveTo(...points[0]);// path.rect(...points[1], ...points[2]);path.closePath()return path;};draggable(chartElement, points, labels, lines, draw, {fill: 'orange'});}function drag() {function dragstarted(event, d) {// console.log(d)// d3Selection.select(this).raise().attr("stroke", "black");}function dragged(event, d) {// console.log(d)// d3Selection.select(this).attr("cx", d.x = event.x).attr("cy", d.y = event.y);}function dragended(event, d) {// d3Selection.select(this).attr("stroke", null);}return d3.drag().on("start", dragstarted).on("drag", dragged).on("end", dragended);}freshSvg()function update(chart, points, labels, lines, draw, options) {d3.select(chart).select(".u-path").style("stroke", "orange").style("fill", options ? (options.fill ? options.fill : "none") : "none").attr("d", draw());d3.select(chart).selectAll(".u-point").style("stroke", "orange").style("fill", "orange").data(points).join(enter =>enter.append("g").classed("u-point", true).call(g => {g.append("circle").attr("r", 3);g.append("text").text((d, i) => labels[i]).attr("dy", d => (d[1] > 100 ? 15 : -5));})).attr("transform", d => `translate(${d})`);d3.select(chart).selectAll(".u-line").style("stroke", "#aaa").style("stroke-dasharray", "2 2").data(lines).join("line").attr("x1", d => d[0][0]).attr("y1", d => d[0][1]).attr("x2", d => d[1][0]).attr("y2", d => d[1][1]).classed("u-line", true);}function draggable(chart, points, labels, lines, draw, options) {update(chart, points, labels, lines, draw, options);const dist = (p, m) => {return Math.sqrt((p[0] - m[0]) ** 2 + (p[1] - m[1]) ** 2);};var subject, dx, dy;function dragSubject(event) {const p = d3.pointer(event.sourceEvent, chart);subject = d3.least(points, (a, b) => dist(p, a) - dist(p, b));if (dist(p, subject) > 48) subject = null;if (subject)d3.select(chart).style("cursor", "hand").style("cursor", "grab");else d3.select(chart).style("cursor", null);return subject;}d3.select(chart).on("mousemove", event => dragSubject({sourceEvent: event})).call(d3.drag().subject(dragSubject).on("start", event => {if (subject) {d3.select(chart).style("cursor", "grabbing");dx = subject[0] - event.x;dy = subject[1] - event.y;}}).on("drag", event => {if (subject) {subject[0] = event.x + dx;subject[1] = event.y + dy;}}).on("end", () => {d3.select(chart).style("cursor", "grab");}).on("start.render drag.render end.render", () =>update(chart, points, labels, lines, draw, options)));}</script>
</html>