利用html5实现canvas海底水草动画特效



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特效描述:利用html5实现 canvas海底水草动画特效,利用html5实现canvas海底水草动画特效

代码结构

1. HTML代码

<canvas></canvas>
<script>
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();
}
function Stem(points, color) {
  this.points = points;
  this.color = color;
}
Stem.prototype.draw = function(ctx) {
  var len, ctrlPoint, point;
  len = this.points.length - 1;
  ctrlPoint = {x: 0, y: 0};
  ctx.save();
  ctx.strokeStyle = this.color;
  ctx.beginPath();
  ctx.moveTo(this.points[this.points.length - 1].x, this.points[this.points.length - 1].y);
  for (var i = len; i >= 1; i--) {
    point = this.points[i];
    ctrlPoint.x = (point.x + this.points[i - 1].x) / 2;
    ctrlPoint.y = (point.y + this.points[i - 1].y) / 2;
    ctx.quadraticCurveTo(point.x, point.y, ctrlPoint.x, ctrlPoint.y);
    ctx.lineWidth = i * 1.1;
    ctx.stroke();
    ctx.fillStyle = 'red';
  }
  ctx.restore();
}
init();
function init(){
  canvas = document.querySelector('canvas');
  ctx = canvas.getContext('2d');
  width = canvas.width = window.innerWidth;
  height = canvas.height = window.innerHeight;
  populateStems(height / 3, width, 25);
  generateBubbles(50);
  drawFrame();
};
function generateBubbles(bubblesLimit) {
  for (var i = 0; i <= bubblesLimit; i++) {
    bubbles.push(new Bubble(Math.random() * width, height + Math.random() * height / 2, 2 + Math.random() * 2));
  }
}
function populateStems(offset, limit, step) {
  for (var x = 0; x <= limit; x += step) {
    generateStem(x, height / 2 - offset / 2 + Math.random() * offset, 50)
  }
}
function generateStem(x, pointsLen, step) {
  var positions, y, offset, colorsArr, color;
  colorsArr = ['#6e881b', '#5d7314', '#54690f', '#657f0f', '#6f8f06'];
  color = Math.floor(1 + Math.random() * colorsArr.length - 1);
  positions = [];
  if (height < 600) {
  	offset = -40 + Math.random() * 80;
    for (y = height - pointsLen; y <= height + 100; y += step / 2) {
      positions.push({x: x + offset / (y / 2000), y: y, angle: Math.random() * 360, speed: 0.1 + Math.random() * 0.3});
    }
  } else {
  	offset = -100 + Math.random() * 200;
    for (y = height - pointsLen; y <= height + 100; y += step) {
      positions.push({x: x + offset / (y / 2000), y: y, angle: Math.random() * 360, speed: 0.1 + Math.random() * 0.3});
    }
  }
  stems.push(new Stem(positions, colorsArr[color]));
}
function drawFrame() {
  window.requestAnimationFrame(drawFrame, canvas);
  ctx.fillStyle = '#17293a';
  ctx.fillRect(0, 0, width, height);
  bubbles.forEach(moveBubble);
  stems.forEach(function(stem) {
    stem.points.forEach(movePoint);
    stem.draw(ctx);
  });
}
function moveBubble(bubble) {
  if (bubble.y + bubble.radius <= 0) bubble.y = bubble.oldY;
  bubble.y += bubble.vy;
  bubble.draw(ctx);
}
function movePoint(point, index) {
  point.x += Math.sin(point.angle) / (index / 2.2);
  point.angle += point.speed;
}
</script>



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