canvas绘制正三边形，正四边形，正五边形...正N边形

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如何使用canvas绘制正三边形，正四边形，正五边形…正N边形呢？这里封装了一个函数regulaPolygon(cxt, n, dx, dy, R, angle, djs_fillColor, djs_strokeColor)，可以设定不同的值，来产生不同正多边形。

示例效果图

示例源代码（共94行）

/*
* @Author: 大剑师兰特（xiaozhuanlan），还是大剑师兰特（CSDN）
* @此源代码版权归大剑师兰特所有，可供学习或商业项目中借鉴，未经授权，不得重复地发表到博客、论坛，问答，git等公共空间或网站中。
* @Email: 2909222303@qq.com
* @weixin: gis-dajianshi
* @First published in CSDN
* @First published time: 2024-01-21
*/
<template>
	<div class="djs_container">
		<div class="top">
			<h3>canvas绘制正N边形</h3>
			<div>大剑师兰特, 还是大剑师兰特，gis-dajianshi</div>
			<h4>
				<el-button type="primary" size="mini" @click="draw()">正多边形</el-button>
				<el-button type="danger" size="mini" @click="clearCanvas()">清除</el-button>
			</h4>
		</div>
		<div class="dajianshi ">
			<canvas id="dajianshi" ref="mycanvas" width="980" height="490"></canvas>
		</div>
	</div>
</template>
<script>
	export default {
		data() {
			return {
				ctx: null,
				canvas: null,
			}
		},
		mounted() {
			this.setCanvas()
		},
		methods: {
			clearCanvas() {
				this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
			},
			setCanvas() {
				this.canvas = document.getElementById('dajianshi');
				if (!this.canvas.getContext) return;
				this.ctx = this.canvas.getContext("2d");
			},
			draw() {
				this.regulaPolygon(this.ctx, 3, 100, 245, 70, -10, 'red', 'black');
				this.regulaPolygon(this.ctx, 4, 250, 245, 70, 10, 'orange', 'black');
				this.regulaPolygon(this.ctx, 5, 400, 245, 70, 20, 'yellow', 'black');
				this.regulaPolygon(this.ctx, 6, 550, 245, 70, -20, 'green', 'black');
				this.regulaPolygon(this.ctx, 7, 700, 245, 70, 90, 'blue', 'black');
				this.regulaPolygon(this.ctx, 8, 850, 245, 70, 90, 'purple', 'black');

			},

			//边数n中心点dx,中心点dy,半径R,旋转角度angle
			regulaPolygon(cxt, n, dx, dy, R, angle, djs_fillColor, djs_strokeColor) {
				cxt.beginPath();
				let degree = (2 * Math.PI) / n;
				let rangle = (angle * 2 * Math.PI) / 360;
				for (let i = 0; i < n; i++) {
					let x = Math.cos(i * degree - rangle);
					let y = Math.sin(i * degree - rangle);
					cxt.lineTo(x * R + dx, y * R + dy);
				}
				cxt.closePath();
				cxt.fillStyle = djs_fillColor;
				cxt.fill();
				cxt.strokeStyle = djs_strokeColor;
				cxt.stroke();
			}
		}
	}
</script>
<style scoped>
	.djs_container {
		width: 1000px;
		height: 680px;
		margin: 50px auto;
		border: 1px solid #991188;
		position: relative;
	}

	.top {
		margin: 0 auto 0px;
		padding: 10px 0;
		background: #991188;
		color: #fff;
	}

	.dajianshi {
		margin: 5px auto 0;
		border: 1px solid #ccc;
		width: 980px;
		height: 490px;
		background-color: #f9f9f9;
	}
</style>

canvas基本属性

属性	属性	属性
canvas	fillStyle	filter
font	globalAlpha	globalCompositeOperation
height	lineCap	lineDashOffset
lineJoin	lineWidth	miterLimit
shadowBlur	shadowColor	shadowOffsetX
shadowOffsetY	strokeStyle	textAlign
textBaseline	width

canvas基础方法

方法	方法	方法
arc()	arcTo()	addColorStop()
beginPath()	bezierCurveTo()	clearRect()
clip()	close()	closePath()
createImageData()	createLinearGradient()	createPattern()
createRadialGradient()	drawFocusIfNeeded()	drawImage()
ellipse()	fill()	fillRect()
fillText()	getImageData()	getLineDash()
isPointInPath()	isPointInStroke()	lineTo()
measureText()	moveTo()	putImageData()
quadraticCurveTo()	rect()	restore()
rotate()	save()	scale()
setLineDash()	setTransform()	stroke()
strokeRect()	strokeText()	transform()
translate()