如何用html画出一个烟花？

发布时间：2024年01月22日

问题描述：如何用html画出一个烟花？

问题解答：

将下面代码复制到一个txt文件中，然后修改后缀txt→html，用浏览器打开就是烟花了。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <TITLE> New Document </TITLE>
  <META NAME="Generator" CONTENT="EditPlus">
  <META NAME="Author" CONTENT="">
  <META NAME="Keywords" CONTENT="">
  <META NAME="Description" CONTENT="">
  <style>
  body: {
	padding: 0;
}

canvas {
	display: block;
}
  </style>
 </HEAD>

 <BODY>
 <canvas id="canvas"></canvas>
<script src="https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js"></script>
  <script>
  $(function() {
	var canvas = $('#canvas')[0];
	canvas.width = $(window).width();
	canvas.height = $(window).height();
	var ctx = canvas.getContext('2d');
	
	// resize
	$(window).on('resize', function() {
		canvas.width = $(window).width();
		canvas.height = $(window).height();
		ctx.fillStyle = '#000';
		ctx.fillRect(0, 0, canvas.width, canvas.height);
	});

	// init
	ctx.fillStyle = '#000';
	ctx.fillRect(0, 0, canvas.width, canvas.height);
	// objects
	var listFire = [];
	var listFirework = [];
	var fireNumber = 10;
	var center = { x: canvas.width / 2, y: canvas.height / 2 };
	var range = 100;
	for (var i = 0; i < fireNumber; i++) {
		var fire = {
			x: Math.random() * range / 2 - range / 4 + center.x,
			y: Math.random() * range * 2 + canvas.height,
			size: Math.random() + 0.5,
			fill: '#fd1',
			vx: Math.random() - 0.5,
			vy: -(Math.random() + 4),
			ax: Math.random() * 0.02 - 0.01,
			far: Math.random() * range + (center.y - range)
		};
		fire.base = {
			x: fire.x,
			y: fire.y,
			vx: fire.vx
		};
		//
		listFire.push(fire);
	}

	function randColor() {
		var r = Math.floor(Math.random() * 256);
		var g = Math.floor(Math.random() * 256);
		var b = Math.floor(Math.random() * 256);
		var color = 'rgb($r, $g, $b)';
		color = color.replace('$r', r);
		color = color.replace('$g', g);
		color = color.replace('$b', b);
		return color;
	}

	(function loop() {
		requestAnimationFrame(loop);
		update();
		draw();
	})();

	function update() {
		for (var i = 0; i < listFire.length; i++) {
			var fire = listFire[i];
			//
			if (fire.y <= fire.far) {
				// case add firework
				var color = randColor();
				for (var i = 0; i < fireNumber * 5; i++) {
					var firework = {
						x: fire.x,
						y: fire.y,
						size: Math.random() + 1.5,
						fill: color,
						vx: Math.random() * 5 - 2.5,
						vy: Math.random() * -5 + 1.5,
						ay: 0.05,
						alpha: 1,
						life: Math.round(Math.random() * range / 2) + range / 2
					};
					firework.base = {
						life: firework.life,
						size: firework.size
					};
					listFirework.push(firework);
				}
				// reset
				fire.y = fire.base.y;
				fire.x = fire.base.x;
				fire.vx = fire.base.vx;
				fire.ax = Math.random() * 0.02 - 0.01;
			}
			//
			fire.x += fire.vx;
			fire.y += fire.vy;
			fire.vx += fire.ax;
		}

		for (var i = listFirework.length - 1; i >= 0; i--) {
			var firework = listFirework[i];
			if (firework) {
				firework.x += firework.vx;
				firework.y += firework.vy;
				firework.vy += firework.ay;
				firework.alpha = firework.life / firework.base.life;
				firework.size = firework.alpha * firework.base.size;
				firework.alpha = firework.alpha > 0.6 ? 1 : firework.alpha;
				//
				firework.life--;
				if (firework.life <= 0) {
					listFirework.splice(i, 1);
				}
			}
		}
	}

	function draw() {
		// clear
		ctx.globalCompositeOperation = 'source-over';
		ctx.globalAlpha = 0.18;
		ctx.fillStyle = '#000';
		ctx.fillRect(0, 0, canvas.width, canvas.height);

		// re-draw
		ctx.globalCompositeOperation = 'screen';
		ctx.globalAlpha = 1;
		for (var i = 0; i < listFire.length; i++) {
			var fire = listFire[i];
			ctx.beginPath();
			ctx.arc(fire.x, fire.y, fire.size, 0, Math.PI * 2);
			ctx.closePath();
			ctx.fillStyle = fire.fill;
			ctx.fill();
		}

		for (var i = 0; i < listFirework.length; i++) {
			var firework = listFirework[i];
			ctx.globalAlpha = firework.alpha;
			ctx.beginPath();
			ctx.arc(firework.x, firework.y, firework.size, 0, Math.PI * 2);
			ctx.closePath();
			ctx.fillStyle = firework.fill;
			ctx.fill();
		}
	}
})
  </script>
 </BODY>
</HTML>

效果如下：

文章来源:https://blog.csdn.net/weixin_43501408/article/details/135742394
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