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

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;

}