html5 canvas海底水草动画特效

html5 canvas海底水草动画特效是一款深海底冒泡的海藻动画场景特效

var canvas, ctx, width, height, stems, bubbles;

stems = [];
bubbles = [];

function Bubble(x, y, radius) {
  this.x = x;
  this.y = y;
  this.radius = radius;
  this.vy = -Math.random() * 5;
  this.opacity = 0.2 + Math.random() * 0.5;
  this.oldY = y;
}

Bubble.prototype.draw = function() {
  var strokeColor, fillColor;

  strokeColor = 'rgba(255, 255, 255,' + this.opacity  + ')';
  fillColor = 'rgba(255, 255, 255,' + (this.opacity / 2) + ')';

  ctx.save();
  ctx.lineWidth = 0.8;
  ctx.strokeStyle = strokeColor;
  ctx.fillStyle = fillColor;
  ctx.beginPath();
  ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
  ctx.closePath();
  ctx.fill();
  ctx.stroke();
  ctx.restore();
}