JavaScript 波浪
【摘要】
<html>
<head>
<meta charset="utf8"/>
<title>波浪</title&g...
<html>
<head>
<meta charset="utf8"/>
<title>波浪</title>
<style>
#canvas {
border: 1px solid #d3d3d3;
float:left;
}
span {
float:left;
margin-left: 10px;
}
</style>
</head>
<body>
<canvas id="canvas" width="200" height="200">Your browser does not support the HTML5 canvas tag.</canvas>
<script>
function onGlobalCompositeOperationChange() {
window.mGlobalCompositeOperation = event.target.options[event.target.options.selectedIndex].innerHTML;
}
</script>
<span>
混合效果:<br/>
<select id="globalCompositeOperationSelect" onchange="onGlobalCompositeOperationChange()">
<option selected="selected">none</option>
<option>source-over</option>
<option>source-atop</option>
<option>source-in</option>
<option>source-out</option>
<option>destination-over</option>
<option>destination-atop</option>
<option>destination-in</option>
<option>destination-out</option>
<option>lighter</option>
<option>copy</option>
<option>xor</option>
</select>
</span>
<script>
(function () {
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
var image = new Image();
image.src = "chrome.png";
//波峰或波谷的高度
var waveHeight = 8;
//要显示的波浪个数
var waveCount = 5;
//波长，即两波峰(波谷)之间的距离
var waveLen = c.width / waveCount;
//半波长
var halfWaveLen = waveLen / 2;
//四风之一波长
var quarterWaveLen = halfWaveLen / 2;
//进度条更新步长
var progressStep = 1;
//水平位移步长
var stepX = 1;
//垂直位移步长，容器除以100份，每一份的高度
var stepY = c.height / 100;
//为了让波浪全部消失，必须添加一点额外的进度
var additionProgress = waveHeight / stepY;
//当前波浪起始点X坐标
var startX = -1 * waveLen;
//当前水平面高度
var waterHeight;
//当前进度值(0-100)
var progress;
//当前X坐标
var currentX;
//波峰
var peakY;
//波谷
var troughY;
//绘制颜色
var color;
//hsl
var hue;
var saturation;
var luminance = "50%";
//返回一个随机的RGB颜色
function randomRGBColor() {
return "rgb(" + Math.round(Math.random() * 255) + "," + Math.round(Math.random() * 255) + "," + Math.round(Math.random() * 255) + ")";
}
//生成随机色相
function randomHue() {
hue = Math.round(Math.random() * 360);
}
//组合成HSL颜色(注意：SL只能用百分号的形式，小数的形式不合法)
function formHSLColor() {
saturation = getProgress() + "%";
return "hsl(" + hue + "," + saturation + "," + luminance + ")";
}
//根据当前进度，计算水平面高度
function calcWaterHeight() {
return (100 - progress) * stepY;
}
//更新
function update() {
startX += stepX;
progress += progressStep;
waterHeight = calcWaterHeight();
currentX = startX;
peakY = waterHeight - waveHeight;
troughY = waterHeight + waveHeight;
if (progress > 100 + additionProgress) {
progressStep *= -1;
}
if (progress < 0 - additionProgress) {
progressStep *= -1;
//color = randomRGBColor();
randomHue();
}
color = formHSLColor();
if (startX >= 0) {
startX = -1 * waveLen;
}
}
//如果是外部要获取当前进度值，必须使用处理之后的progress返回
function getProgress() {
return progress < 0 ? 0 : (progress > 100 ? 100 : progress);
}
//渲染
function render() {
ctx.globalCompositeOperation = "source-over";
ctx.clearRect(0, 0, c.width, c.height);
ctx.fillStyle = color;
ctx.beginPath();
ctx.moveTo(currentX, waterHeight);
for(var i = 0; i < waveCount + 1; i++, currentX += waveLen) {
//绘制波谷
ctx.quadraticCurveTo(currentX + quarterWaveLen, troughY, currentX + halfWaveLen, waterHeight);
//绘制波峰
ctx.quadraticCurveTo(currentX + quarterWaveLen + halfWaveLen, peakY, currentX + waveLen, waterHeight);
}
ctx.lineTo(c.width, c.height);
ctx.lineTo(0, c.height);
ctx.closePath();
ctx.fill();
if(window.mGlobalCompositeOperation !== undefined && window.mGlobalCompositeOperation !== "none") {
ctx.globalCompositeOperation = window.mGlobalCompositeOperation;
ctx.drawImage(image, 0, 0, c.width, c.height);
}
}
//循环
function loop() {
update();
render();
requestAnimationFrame(loop);
}
//初始化
function init() {
progress = 0;
//color = randomRGBColor();
randomHue();
color = formHSLColor();
waterHeight = calcWaterHeight();
loop();
}
init();
})();
</script>
</body>
</html>
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文章来源: blog.csdn.net，作者：福州-司马懿，版权归原作者所有，如需转载，请联系作者。
原文链接：blog.csdn.net/chy555chy/article/details/54406071
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