canvas实现的粒子效果背景

html5 canvas 实现网页背景粒子效果canvasConfig = canvasConfig || {};
var html = getElementByTag("html")[0];
// 获取body作为背景
// var body = getElementByTag("body")[0];

// 获取特定div作为背景
// mydiv是你想要将其作为背景的div的ID
var body = document.getElementById("mydiv");
var canvasObj = document.createElement("canvas");

var canvas = {
element: canvasObj,
points : [],
// 默认配置
config: {
vx: canvasConfig.vx || 4,
vy:  canvasConfig.vy || 4,
height: canvasConfig.height || 2,
width: canvasConfig.width || 2,
count: canvasConfig.count || 100,
color: canvasConfig.color || "121, 162, 185",
stroke: canvasConfig.stroke || "130,255,255",
dist: canvasConfig.dist || 6000,
e_dist: canvasConfig.e_dist || 20000,
max_conn: 10
}
};

// 获取context
if(canvas.element.getContext("2d")){
canvas.context = canvas.element.getContext("2d");
}else{
return null;
}

body.style.padding = "0";
body.style.margin = "0";
// body.replaceChild(canvas.element, canvasDiv);
body.appendChild(canvas.element);

canvas.element.style = "position: fixed; top: 0; left: 0; z-index: -1;";
canvasSize(canvas.element);
window.onresize = function(){
canvasSize(canvas.element);
}
body.onmousemove = function(e){
var event = e || window.event;
canvas.mouse = {
x: event.clientX,
y: event.clientY
}
}
document.onmouseleave = function(){
canvas.mouse = undefined;
}
setInterval(function(){
drawPoint(canvas);
}, 40);