function siriwave(opt) {
    this.opt = opt || {};
    this.k = 1;
    this.f = 6;
    this.speed = this.opt.speed || 0.1;
    this.noise = this.opt.noise || 0;
    this.phase = this.opt.phase || 0;
    if (!devicepixelratio) devicepixelratio = 1;
    this.width = devicepixelratio * (this.opt.width || 320);
    this.height = devicepixelratio * (this.opt.height || 200);
    this.max = (this.height / 2) - 4;
    this.canvas = document.createelement('canvas');
    this.canvas.id = "xin_wave";
    this.canvas.width = this.width;
    this.canvas.height = this.height;
    this.canvas.style.width = (this.width / devicepixelratio) + 'px';
    this.canvas.style.height = (this.height / devicepixelratio) + 'px';
    if (document.getelementsbyclassname("xin_dong").length != 0) {
        for (var i = 0; i < document.getelementsbyclassname("xin_dong").length; i++) {
            document.getelementsbyclassname("xin_dong")[i].appendchild(this.canvas);
        }
    }
    this.ctx = this.canvas.getcontext('2d');
    this.run = false;
}
siriwave.prototype = {
    _globalattenuationfn: function(x) {
        return math.pow(this.k * 4 / (this.k * 4 + math.pow(x, 4)), this.k * 2);
    },
    _drawline: function(attenuation, color, width) {
        this.ctx.moveto(0, 0);
        this.ctx.beginpath();
        this.ctx.strokestyle = color;
        this.ctx.linewidth = width || 0.5;
        var x, y;
        for (var i = -this.k; i <= this.k; i += 0.01) {
            x = this.width * ((i + this.k) / (this.k * 2));
            y = this.height / 2 + this.noise * this._globalattenuationfn(i) * (1 / attenuation) * math.sin(this.f * i - this.phase);
            this.ctx.lineto(x, y);
        }
        this.ctx.stroke();
    },
    _clear: function() {
        this.ctx.globalcompositeoperation = 'destination-out';
        this.ctx.fillrect(0, 0, this.width, this.height);
        this.ctx.globalcompositeoperation = 'source-over';
    },
    _draw: function() {
        if (!this.run) return;
        this.phase = (this.phase + this.speed) % (math.pi * 64);
        this._clear();
        this._drawline(-5, 'rgba(0,0,0,0.04)');
        this._drawline(-4, 'rgba(0,0,0,0.06)');
        this._drawline(-3, 'rgba(0,0,0,0.08)');
        this._drawline(-2, 'rgba(0,0,0,0.1)');
        this._drawline(-1.6, 'rgba(0,0,0,0.2)');
        requestanimationframe(this._draw.bind(this), 1000);
    },
    start: function() {
        this.phase = 0;
        this.run = true;
        this._draw();
    },
    stop: function() {
        this.run = false;
        this._clear();
    },
    setnoise: function(v) {
        this.noise = math.min(v, 1) * this.max;
    },
    setspeed: function(v) {
        this.speed = v;
    },
    set: function(noise, speed) {
        this.setnoise(noise);
        this.setspeed(speed);
    },
};
var sw = new siriwave({
    width: 1920,
    height: 200
});
sw.setspeed(0.03);
sw.setnoise(0.7);
sw.start();