马上就要过元宵节了，可是大城市是不允许燃放烟花这种空气污染的东西的。有没有很想念小时候在自家院子里放花的快乐时光呢。别急，下面就让小编教大家制作程序员的小浪漫----烟火
情景梳理
- 烟花都是在天空中绽放，我们用幕布与模拟天空 -- canvas
- 烟花绽放时，从一个中心点开始绽放
- 烟花绽放时呈“放射状”
- 烟花绽放后，会有一个缓慢下落的过程，直至消失
烟花幕布
先新建一个和网页可视区大小一样的canvas，并且通过监听显示区的resize事件，来改变canvas的大小。
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);
}
烟花粒子
烟花都是从一个点爆炸，伴随着不同的弧度散开，所以我们先绘制几个小圆点，环绕着一个圆心。有点像loading的小圈圈。这其实就是烟花最开始的状态...
document.addEventListener('mousedown', mouseDownHandler, false);
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();
}
}
效果如下
烟花绽放
var radius = 0;
function fire(x, y) {
createFireworks(x, y);
function tick() {
context.globalCompositeOperation = 'source-over';
context.fillStyle = 'rgba(0,0,0,' + 10 / 100 + ')';
context.fillRect(0, 0, canvas.width, canvas.height);
context.globalCompositeOperation = 'lighter';
drawFireworks();
radius = requestAnimationFrame(tick);
}
cancelAnimationFrame(radius);
tick();
}
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);
}
}
再修改一下mouseDownHandler函数
function mouseDownHandler(e) {
var x = e.clientX;
var y = e.clientY;
fire(x, y)
}
function drawFireworks(sx, sy) {
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 / 300;
p.alpha -= 0.006;
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();
}
}
效果如下
烟花书签
到这以为就玩了，No。还有更惊喜的，还可以让你在chrome中任意网页实现烟花绽放呢
效果图
源码
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 = 'source-over';
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 / 300;
p.alpha -= 0.006;
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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