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HTML5 uses canvas to achieve the flame effect that follows the cursor.

不言Original: 2018-07-03 10:15:022124browse

This example uses the HTML5 canvas element to display a beating flame on the screen through Javascript. The flame will follow the cursor.

The complete code for this effect is as follows. You can also view it by saving the code to an HTML file and opening it. As a result, the flame will follow the cursor:

<!DOCTYPE HTML>
<head>
<meta charset=utf-8" />
<title>HTML5 Canvas火焰效果</title>
<style type="text/css">
body{margin: 0; padding: 0;}
#canvas-keleyi-com {display: block;}
</style>
</head>
<body>
<canvas id="canvas-keleyi-com"></canvas>
<script type="text/javascript">
window.onload = function(){
var keleyi_canvas = document.getElementById("canvas-kel"+"eyi-com");
var ctx = keleyi_canvas.getContext("2d");
var W = window.innerWidth, H = window.innerHeight;
keleyi_canvas.width = W;
keleyi_canvas.height = H;</p>
<p>var particles = [];
var mouse = {};</p>
<p>//Lets create some particles now
var particle_count = 100;
for(var i = 0; i < particle_count; i++)
{
particles.push(new particle());
}
keleyi_canvas.addEventListener(&#39;mousemove&#39;, track_mouse, false);</p>
<p>function track_mouse(e)
{
mouse.x = e.pageX;
mouse.y = e.pageY;
}</p>
<p>function particle()
{
this.speed = {x: -2.5+Math.random()*5, y: -15+Math.random()*10};
//location = mouse coordinates
//Now the flame follows the mouse coordinates
if(mouse.x && mouse.y)
{
this.location = {x: mouse.x, y: mouse.y};
}
else
{
this.location = {x: W/2, y: H/2};
}
//radius range = 10-30
this.radius = 10+Math.random()*20;
//life range = 20-30
this.life = 20+Math.random()*10;
this.remaining_life = this.life;
//colors
this.r = Math.round(Math.random()*255);
this.g = Math.round(Math.random()*255);
this.b = Math.round(Math.random()*255);
}</p>
<p>function draw()
{
ctx.globalCompositeOperation = "source-over";
ctx.fillStyle = "black";
ctx.fillRect(0, 0, W, H);
ctx.globalCompositeOperation = "lighter";</p>
<p>for(var i = 0; i < particles.length; i++)
{
var p = particles[i];
ctx.beginPath();
p.opacity = Math.round(p.remaining_life/p.life*100)/100
var gradient = ctx.createRadialGradient(p.location.x, p.location.y, 0, p.location.x, p.location.y, p.radius);
gradient.addColorStop(0, "rgba("+p.r+", "+p.g+", "+p.b+", "+p.opacity+")");
gradient.addColorStop(0.5, "rgba("+p.r+", "+p.g+", "+p.b+", "+p.opacity+")");
gradient.addColorStop(1, "rgba("+p.r+", "+p.g+", "+p.b+", 0)");
ctx.fillStyle = gradient;
ctx.arc(p.location.x, p.location.y, p.radius, Math.PI*2, false);
ctx.fill();</p>
<p>
p.remaining_life--;
p.radius--;
p.location.x += p.speed.x;
p.location.y += p.speed.y;</p>
<p>if(p.remaining_life < 0 || p.radius < 0)
{
particles[i] = new particle();
}
}
}</p>
<p>setInterval(draw, 86);
}
</script>
</body>
</html>

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