前言

这是一个前端随机生成图片的组件，可以用作滑块验证组件的背景图。

效果

• 以下效果是结合滑块验证组件一起构建的。

代码

<template>
	<img ref="random-image" />
</template>
<script>
export default {
	name: "RandomImg",
	props: {
		width: {
			type: Number,
			default: 400
		},
		height: {
			type: Number,
			default: 220
		}
	},
	mounted() {
		this.init()
	},
	methods: {
		// 生成随机颜色
		getRandomColor() {
			const r = Math.floor(Math.random() * 255)
			const g = Math.floor(Math.random() * 255)
			const b = Math.floor(Math.random() * 255)
			const a = Math.random()
			const color = `rgba(${r}, ${g}, ${b}, ${a})`
			return color
		},
		// 生成随机图案
		getRandomPattern(ctx) {
			const random = Math.floor(Math.random() * 3 + 1)
			if (random == 1) {
				const rectr = Math.floor(Math.random() * 2)
				const rectx = Math.floor(Math.random() * this.width)
				const recty = Math.floor(Math.random() * this.height)
				const rectwidth = Math.floor(Math.random() * this.width)
				const rectheight = Math.floor(Math.random() * this.height)
				if (rectr == 0) {
					ctx.beginPath()
					ctx.strokeStyle = this.getRandomColor()
					ctx.strokeRect(rectx, recty, rectwidth, rectheight)
					ctx.closePath()
				} else {
					ctx.beginPath()
					ctx.fillStyle = this.getRandomColor()
					ctx.fillRect(rectx, recty, rectwidth, rectheight)
					ctx.closePath()
				}
			} else if (random == 2) {
				var arcr = Math.floor(Math.random() * 2)
				var arcx = Math.floor(Math.random() * this.width)
				var arcy = Math.floor(Math.random() * this.height)
				var arcr = Math.floor(Math.random() * this.height)
				if (arcr == 0) {
					ctx.beginPath()
					ctx.strokeStyle = this.getRandomColor()
					ctx.arc(arcx, arcy, arcr, 0, 2 * Math.PI, false)
					ctx.stroke()
					ctx.closePath()
				} else {
					ctx.beginPath()
					ctx.fillStyle = this.getRandomColor()
					ctx.arc(arcx, arcy, arcr, 0, 2 * Math.PI, false)
					ctx.fill()
					ctx.closePath()
				}
			} else if (random == 3) {
				var movex = Math.floor(Math.random() * this.width)
				var movey = Math.floor(Math.random() * this.height)
				var linex = Math.floor(Math.random() * this.width)
				var liney = Math.floor(Math.random() * this.height)
				var linew = Math.floor(Math.random() * this.height / 5)
				ctx.beginPath()
				ctx.strokeStyle = this.getRandomColor()
				ctx.moveTo(movex, movey)
				ctx.lineTo(linex, liney)
				ctx.lineWidth = linew
				ctx.stroke()
				ctx.closePath()
			}
			return ctx
		},
		// canvas转image
		canvasToImage(cvs) {
			const imgDom = this.$refs['random-image']
			imgDom.src = cvs.toDataURL('image/png')
		},
		// 初始化
		init() {
			const canvas = document.createElement('canvas')
			canvas.width = this.width
			canvas.height = this.height
			let context = canvas.getContext('2d')
			context.fillStyle = '#ccc'
			context.fillRect(0, 0, this.width, this.height)
			for (let i = 0; i < 10; i++) {
				context = this.getRandomPattern(context)
			}
			this.canvasToImage(canvas)
		},
		// 刷新图片
		refresh() {
			this.init()
		}
	}
}
</script>
<style scoped>
* {
	user-select: none;
}
</style>