js实现烟花效果

先创建一个Canvas

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

function resizeCanvas() {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
}

function clearCanvas(){
	context.fillStyle = '#ffffff';
	context.fillRect(0,0,canvas.width, canvas.height);
}

window.addEventListener('resize', resizeCanvas, false);
resizeCanvas();

绘制小圆点

function mouseDownHandler(e) {
    var x = e.clientX;
    var y = e.clientY;

    drawFireworks(x,y);
}

function drawFireworks(sx,sy) {
    var count = 10;//烟花粒子数量
    var radius = 10;//烟花环绕半径

    for(var i = 0 ;i<count;i++){
        var angle = 360/count*i;//烟花粒子角度
        var radians = angle * Math.PI / 180;//烟花粒子弧度

        var vx = sx+Math.cos(radians) * radius;
        var vy = sy+Math.sin(radians) * radius;

        var size = 2;
        context.beginPath();
        context.arc(vx, vy, size, 0, Math.PI*2, false)
        context.closePath();
        context.fillStyle = "#ff0000";
        context.fill();
    }
}

document.addEventListener('mousedown', mouseDownHandler, false);

动起来1、

var radius = 0;//圆心半径
function fire(x,y){
    function tick() {
        drawFireworks(x,y);//绘制烟花
        radius++;//半径不断变大
    }
    setInterval(tick,30);//每30毫秒绘制一次
}

动起来2、

var radius = 0;
function fire(x,y){
    function tick() {
        drawFireworks(x,y);
        radius++;
        requestAnimationFrame(tick);
    }
    tick();
}

但真实的烟花肯定不会这么听话，规规矩矩的保持弧度和速度，所以我们要加入一些随机因子。

var rid;
function fire(x,y){
    createFireworks(x,y);

    function tick() {
        drawFireworks();
        rid=requestAnimationFrame(tick);
    }
    cancelAnimationFrame(rid);
    tick();
}

var particles=[];
function createFireworks(sx,sy){
    particles=[];

    var hue = Math.floor(Math.random()*51)+150;
    var hueVariance = 30;
    var count = 100;

    for(var i = 0 ;i<count;i++){
        var p = {};

        var angle = Math.floor(Math.random()*360);
        p.radians = angle * Math.PI / 180;
        p.radius = 0;

        p.sx = sx;
        p.sy = sy;

        p.speed = (Math.random()*5)+.4;

        p.size = Math.floor(Math.random()*3)+1;

        p.hue = Math.floor(Math.random()*((hue+hueVariance)-(hue-hueVariance)))+(hue-hueVariance);
        p.brightness = Math.floor(Math.random()*31)+50;
        p.alpha = (Math.floor(Math.random()*61)+40)/100;

        particles.push(p);
    }
}

function drawFireworks() {
    clearCanvas();

    for(var i = 0 ;i<particles.length;i++){
        var p = particles[i];

        p.vx = p.sx+Math.cos(p.radians) * p.radius;
        p.vy = p.sy+Math.sin(p.radians) * p.radius;

        p.radius += 1+p.speed;

        context.beginPath();
        context.arc(p.vx, p.vy, p.size, 0, Math.PI*2, false);
        context.closePath();

        context.fillStyle = 'hsla('+p.hue+', 100%, '+p.brightness+'%, '+100+')';
        context.fill();
    }
}

很绚丽的对不对？现在我们再给它加入一点烟雾拖尾的效果~

function tick() {
	//tips:注意新加入的这4行代码
	context.globalCompositeOperation = 'destination-out';
	context.fillStyle = 'rgba(0,0,0,'+10/100+')';
	context.fillRect(0,0,canvas.width,canvas.height);
	context.globalCompositeOperation = 'lighter';
	//tipsend
	drawFireworks();
	rid=requestAnimationFrame(tick);
}

现在加入一些重力的影响，让烟花粒子的移动速度越来越慢并且慢慢下落消失

var vx = Math.cos(p.radians) * p.radius;
var vy = Math.sin(p.radians) * p.radius + 0.4;

p.x += vx;
p.y += vy;

p.radius *= 1 - p.speed/100;

p.alpha -= 0.005;

在Chrome里新建一个书签，复制以下代码，粘贴到网址一栏，然后保存。

javascript:!(function() {var cdom = document.createElement("canvas");cdom.id = "myCanvas";cdom.style.position="fixed";cdom.style.left = "0";cdom.style.top = "0";cdom.style.zIndex=-1;document.body.appendChild(cdom);var canvas = document.getElementById('myCanvas');var context = canvas.getContext('2d');function resizeCanvas() {canvas.width = window.innerWidth;canvas.height = window.innerHeight;}window.addEventListener('resize', resizeCanvas, false);resizeCanvas();clearCanvas();function clearCanvas(){context.fillStyle = '#000000';context.fillRect(0,0,canvas.width, canvas.height);}function mouseDownHandler(e) {var x = e.clientX;var y = e.clientY;fire(x,y);}var rid;function fire(x,y){createFireworks(x,y);function tick() {context.globalCompositeOperation = 'destination-out';    context.fillStyle = 'rgba(0,0,0,'+10/100+')';    context.fillRect(0,0,canvas.width,canvas.height);    context.globalCompositeOperation = 'lighter';drawFireworks();rid=requestAnimationFrame(tick);}cancelAnimationFrame(rid);tick();}var particles=[];function createFireworks(sx,sy){particles=[];var hue = Math.floor(Math.random()*51)+150;var hueVariance = 30;var count = 100;for(var i = 0 ;i<count;i++){var p = {};var angle = Math.floor(Math.random()*360);p.radians = angle * Math.PI / 180;p.x = sx;p.y = sy;p.speed = (Math.random()*5)+.4;p.radius = p.speed;p.size = Math.floor(Math.random()*3)+1;p.hue = Math.floor(Math.random()*((hue+hueVariance)-(hue-hueVariance)))+(hue-hueVariance);p.brightness = Math.floor(Math.random()*31)+50;p.alpha = (Math.floor(Math.random()*61)+40)/100;particles.push(p);}}function drawFireworks() {clearCanvas();for(var i = 0 ;i<particles.length;i++){var p = particles[i];var vx = Math.cos(p.radians) * p.radius;var vy = Math.sin(p.radians) * p.radius + 0.4;p.x += vx;p.y += vy;p.radius *= 1 - p.speed/100;p.alpha -= 0.005;context.beginPath();context.arc(p.x, p.y, p.size, 0, Math.PI*2, false);context.closePath();context.fillStyle = 'hsla('+p.hue+', 100%, '+p.brightness+'%, '+p.alpha+')';context.fill();}}document.addEventListener('mousedown', mouseDownHandler, false);})();

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转载~