第一次用简书 随便贴点东西#

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简化函数

//返回1-num随机数
function getRandom(num){    
return parseInt(Math.random()*num)+1;}

function getTag(tagName){    
return document.getElementsByTagName(tagName);}
//返回num的平方
function pow(num){ return Math.pow(num,2);}

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初始化参数

<pre>
function canvasInit(Config){
var config=Config||{},
body=getTag("body")[0],
canvasObj=document.createElement("canvas");
//定义参数
var canvas={
element:canvasObj,
points:[],
config:{
vx:config.vx||4, //点的移速
vy:config.vy||4,
height:config.height||2, //点大小
width:config.width||2,
dist:config.dist||6000, //连线的最短距离
e_dist:config.e_dist||20000, //响应鼠标的最短距离
count:config.count||100, //点的数量
max_line:config.max_conn||10, //点的最高连线数
color:config.color||"aqua", //点的颜色
stroke:config.stroke||"lightgreen" //线的颜色
}
};

</pre>

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样式添加与画布大小重绘

<pre>
body.style="margin:0;padding:0;";
canvas.element.style="position:absolute;top:0;left:0;z-index:-1;";
body.appendChild(canvas.element);
//获取2d 设置画布大小
canvas.context=canvas.element.getContext("2d");
convasResize(canvas);
window.onresize=(function () {
convasResize(canvas);
});
//鼠标滑动与离开事件
body.onmousemove=function (e){
var event=e||window.event;
canvas.mouse={
x:event.clientX,
y:event.clientY
};
};
document.onmouseleave=function (){
canvas.mouse=undefined;
};
//调用函数循环执行
(function autoFlush(){
drawPoint(canvas);
setTimeout(function (){
autoFlush();
},40);
})();
}
</pre>

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画布大小函数

<pre>
//重置画布大小
function convasResize(canvas){
canvas.element.width=document.documentElement.clientWidth;
canvas.element.height=document.documentElement.clientHeight;
}
</pre>

===================================================

画点

<pre>
//画点
function drawPoint(canvas){
var context=canvas.context,point;
context.beginPath();
context.clearRect(0,0,canvas.element.width,canvas.element.height);
context.fillStyle=canvas.config.color;
for(var i= 0,len=canvas.config.count;i<len;i++){
if(canvas.points.length!=canvas.config.count){
point={
x:getRandom(canvas.element.width)-1,
y:getRandom(canvas.element.height)-1,
vx:canvas.config.vx/2-getRandom(canvas.config.vx),
vy:canvas.config.vy/2-getRandom(canvas.config.vx)
}
}
//处理边界情况及点移动速率
else{
point=borderPoint(canvas.points[i],canvas);
}
context.fillRect(point.x,point.y,canvas.config.width,canvas.config.height);
canvas.points[i]=point;
}
drawLine(canvas.context,canvas,canvas.mouse);
context.closePath();
}
//边界处理
function borderPoint(point,canvas){
var p=point;
if(p.x<0 || p.x>canvas.element.width){
p.vx= -p.vx;
p.x+= p.vx;
}
else if(p.y<0 || p.y>canvas.element.height){
p.vy= -p.vy;
p.y+= p.vy;
}
else{
p={
x: p.x+ p.vx,
y: p.y+ p.vy,
vx: p.vx,
vy: p.vy
};
}
return p;
}

</pre>

===============================================

画线

<pre>

function drawLine(context,canvas,mouse){
context=context||canvas.context;
for(var i= 0,len=canvas.config.count;i < len;i++){
canvas.points[i].max_line=0;
for(var j=0;j < len;j++){
if(i!=j){
var dist=pow(canvas.points[i].x-canvas.points[j].x,2)+pow(canvas.points[i].y-canvas.points[j].y,2);
if(dist<=canvas.config.dist){
if(canvas.points[i].max_line<=canvas.config.max_line){
canvas.points[i].max_line++;
context.beginPath();
context.lineWidth=0.5-(dist/canvas.config.dist)/2;
context.strokeStyle="rgb("+canvas.config.stroke+")";
context.moveTo(canvas.points[i].x,canvas.points[i].y);
context.lineTo(canvas.points[j].x,canvas.points[j].y);
context.stroke();
}
}
}
}
//鼠标进入
if(mouse){
dist=pow(canvas.points[i].x-mouse.x,2)+pow(canvas.points[i].y-mouse.y,2);
if(dist>canvas.config.dist&&dist < canvas.config.e_dist){
canvas.points[i].x=canvas.points[i].x+(mouse.x - canvas.points[i].x) / 20;
canvas.points[i].y=canvas.points[i].y+(mouse.y - canvas.points[i].y) / 20;
}
if(dist < canvas.config.dist){
context.beginPath();
context.lineWidth=1;
context.strokeStyle="rgb("+canvas.config.stroke+")";
context.moveTo(canvas.points[i].x,canvas.points[i].y);
context.lineTo(mouse.x,mouse.y);
context.stroke();
}
}
}
}

</pre>