在项目中,遇见的一个功能是做搜索任务,页面初始全局仅一个搜索框在正中间,才想到要用粒子光效背景来稍微点缀一下,在网上找到的其他方法,再融合一下。
全局代码如下:
html
<canvas id="bg"></canvas>
js
<script>
initBg();
function initBg(){
var WIDTH = window.innerWidth,HEIGHT = window.innerHeight,POINT = 35;//界面上点的个数
var canvas = document.getElementById("bg");
canvas.width = WIDTH;
canvas.height = HEIGHT;
var context = canvas.getContext("2d");
context.strokeStyle = "rgba(33,133,208,0.8)";
context.strokeWidth = 1;
context.fillStyle = "rgba(33,133,208,0.2)";
var circleArr = [];
var Line = function(x,y,_x,_y,o){
this.beginX = x;
this.beginY = y;
this.closeX = _x;
this.closeY = _y;
this.o = o;
};
var Circle = function(x,y,r,moveX,moveY){
this.x = x;
this.y = y;
this.r = r;
this.moveX = moveX;
this.moveY = moveY;
};
var num = function(max,_min){
var min = arguments[1]||0;
return Math.floor(Math.random()*(max-min+1)+min);
};
var drawCircle = function(ctx,x,y,r,moveX,moveY){
var circle = new Circle(x,y,r,moveX,moveY);
ctx.beginPath();
ctx.arc(circle.x,circle.y,circle.r,0,2*Math.PI);
ctx.closePath();
ctx.fill();
return circle;
};
var drawLine = function(ctx,x,y,_x,_y,o){
var line = new Line(x,y,_x,_y,o);
ctx.beginPath();
ctx.strokeStyle = "rgba(33,133,208,"+o+")";
ctx.moveTo(line.beginX,line.beginY);
ctx.lineTo(line.closeX,line.closeY);
ctx.closePath();
ctx.stroke();
};
var draw = function(){
context.clearRect(0,0,canvas.width,canvas.height);
for(var i = 0;i < POINT;i++){
drawCircle(context,circleArr[i].x,circleArr[i].y,circleArr[i].r);
}
for(var i = 0;i < POINT;i++){
for(var j = 0;j < POINT;j++){
if(i + j < POINT){
var A = Math.abs(circleArr[i+j].x - circleArr[i].x);
var B = Math.abs(circleArr[i+j].y - circleArr[i].y);
var lineLength = Math.sqrt(A*A + B*B);
var C = 1/lineLength*7-0.009;
var lineOpacity = C > 0.3?0.3:C;
if(lineOpacity > 0){
drawLine(context,circleArr[i].x,circleArr[i].y,circleArr[i+j].x,circleArr[i+j].y,lineOpacity);
}
}
}
}
};
var init = function(){
circleArr = [];
for(var i = 0;i < POINT;i++){
circleArr.push(drawCircle(context,num(WIDTH),num(HEIGHT),num(15,2),num(10,-10)/40,num(10,-10)/40));
}
draw();
};
init();
var interval = setInterval(function(){
for(var i = 0;i < POINT;i++){
var cir = circleArr[i];
cir.x += cir.moveX;
cir.y += cir.moveY;
if(cir.x > WIDTH) cir.x = 0;
else if(cir.x < 0) cir.x = WIDTH;
if(cir.y > HEIGHT) cir.y = 0;
else if(cir.y < 0) cir.y = HEIGHT;
}
draw();
});
}
</script>
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