本文介绍如何使用 HTML5 Canvas 绘制饼状图，并通过 JavaScript 代码实现数据可视化。示例包含基础画布设置、扇形绘制逻辑以及动态生成图例的完整流程，供开发者参考学习。
Canvas 饼状图绘制示例
这里展示如何利用 Canvas 元素绘制一个饼状图，供读者参考。
具体实现代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas id='canvas' width='800' height='400' style="border: 1px solid red;"></canvas>
<script>
let data = [
{ title: "服饰1", money: 400 },
{ title: "服饰2", money: 300 },
{ title: "服饰3", money: 400 },
{ title: "服饰4", money: 200 },
{ title: "服饰5", money: 500 },
{ title: "服饰6", money: 180 },
{ title: "服饰7", money: 500 }]
/** @type {HTMLCanvasElement} */
let canvas = document.querySelector("#canvas");
let ctx = canvas.getContext("2d");
let r = 100;
let money = function (obj, sum) {
for (let i = 0; i < obj.length; i++) {
sum += data[i].money
}
return sum;
}
let totalmoney = money(data, 0);
let nowsum = 0;
let start = 0;
let end = 0;
let R = 100;
let i=0;
data.forEach(function (item) {
ctx.beginPath()
nowsum += item.money;
end = (nowsum / totalmoney)
ctx.moveTo(150, 150);
ctx.arc(150, 150, R, start*Math.PI*2, end*Math.PI*2)
start = end;
//产生随机颜色
ctx.fillStyle = '#' + Math.floor(Math.random() * 0xffffff).toString(16);
ctx.rect(350,5+(35*i),30,30);
ctx.font="14px 黑体"
ctx.fillText(item.title,400,25+(35*i))
ctx.strokeStyle = "gray"
ctx.fill();
ctx.stroke();
i++;
})
</script>
</body>
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