svg-二阶贝塞尔曲线
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
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
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直线
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|直线</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" :d="path"/><line class="u-line"/><line class="u-line"/></svg>
</div>
</body>
</html>
初始化SVG和绘制直线
我们使用D3.js的d3.path()方法来创建一条直线,并将其绘制到SVG中。起始点和终点的坐标分别为[100, 200]
和[600, 400]
。
const chartElement = document.getElementById('chartRef')
const x0 = 100, y0 = 200, x = 600, y = 400;function freshSvg() {const path = d3.path();path.moveTo(x0, y0);path.lineTo(x, y);const points = [[x0, y0], [x, y]];const labels = ["开始", "结束"];const lines = [];const draw = () => {const path = d3.path();path.moveTo(...points[0]);path.lineTo(...points[1]);return path;};draggable(chartElement, points, labels, lines, draw);
}freshSvg()
实现拖拽功能
为了让直线的起点和终点可以被拖动,我们需要使用D3.js的拖拽交互模块d3.drag()。通过计算拖拽距离,我们可以实时更新直线的位置:
function draggable(chart, points, labels, lines, draw) {update(chart, points, labels, lines, draw);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)));
}
更新SVG内容
每次拖拽时,我们都需要更新SVG的内容,以反映新的直线位置。这通过update()函数实现,该函数更新路径、控制点和辅助线:
function update(chart, points, labels, lines, draw) {d3.select(chart).select(".u-path").style("stroke", "orange").style("fill", "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(${d})`);d3.select(chart).selectAll(".u-line").style("stroke", "#aaa").style("stroke-dasharray", "2 2").data(lines).join("line").attr("x1", d => d[0][0]).attr("y1", d => d[0][1]).attr("x2", d => d[1][0]).attr("y2", d => d[1][1]).classed("u-line", true);
}
完整实现
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>MyPrint|打印设计|SVG|直线</title><script src="https://cdn.jsdelivr.net/npm/d3@7"></script><script src="./d3-utils.js"></script><style>body {width: 100vw;height: 100vh;margin: 0;display: flex;justify-content: center;align-items: center;}.chart {width: 100%;height: 100%;overflow: visible;}.chart_wrapper {width: 700px;height: 700px;box-shadow: 2px 2px 10px rgba(10, 10, 10, 0.1);border-radius: 10px;}</style>
</head><body>
<div class="chart_wrapper"><svg id="chartRef" class="chart"><path class="u-path" :d="path"/><line class="u-line"/><line class="u-line"/></svg>
</div>
</body><script>const chartElement = document.getElementById('chartRef')const x0 = 100,y0 = 200,x = 600,y = 400;function freshSvg() {const path = d3.path();path.moveTo(x0, y0);path.lineTo(x, y);// 控制点const points = [[x0, y0], [x, y]],// 标题labels = ["开始", "结束"],// 辅助线lines = [],// 绘制方法draw = () => {const path = d3.path();path.moveTo(...points[0]);path.lineTo(...points[1]);return path;};draggable(chartElement, points, labels, lines, draw);}freshSvg()function update(chart, points, labels, lines, draw) {d3.select(chart).select(".u-path").style("stroke", "orange").style("fill", "none").attr("d", draw());d3.select(chart).selectAll(".u-point").style("stroke", "orange").style("fill", "orange").data(points).join(enter =>enter.append("g").classed("u-point", true).call(g => {g.append("circle").attr("r", 3);g.append("text").text((d, i) => labels[i]).attr("dy", d => (d[1] > 100 ? 15 : -5));})).attr("transform", d => `translate(${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) {update(chart, points, labels, lines, draw);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)));}</script>
</html>