第一个方法
;(function(win, lib) {
var doc = win.document;
var docEl = doc.documentElement;
var metaEl = doc.querySelector('meta[name="viewport"]');
var flexibleEl = doc.querySelector('meta[name="flexible"]');
var dpr = 0;
var scale = 0;
var tid;
var flexible = lib.flexible || (lib.flexible = {});
if (metaEl) {
console.warn('将根据已有的meta标签来设置缩放比例');
var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/);
if (match) {
scale = parseFloat(match[1]);
dpr = parseInt(1 / scale);
}
} else if (flexibleEl) {
var content = flexibleEl.getAttribute('content');
if (content) {
var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
if (initialDpr) {
dpr = parseFloat(initialDpr[1]);
scale = parseFloat((1 / dpr).toFixed(2));
}
if (maximumDpr) {
dpr = parseFloat(maximumDpr[1]);
scale = parseFloat((1 / dpr).toFixed(2));
}
}
}
if (!dpr && !scale) {
var isAndroid = win.navigator.appVersion.match(/android/gi);
var isIPhone = win.navigator.appVersion.match(/iphone/gi);
var devicePixelRatio = win.devicePixelRatio;
if (isIPhone) {
// iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
dpr = 3;
} else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)){
dpr = 2;
} else {
dpr = 1;
}
} else {
// 其他设备下，仍旧使用1倍的方案
dpr = 1;
}
scale = 1 / dpr;
}
docEl.setAttribute('data-dpr', dpr);
if (!metaEl) {
metaEl = doc.createElement('meta');
metaEl.setAttribute('name', 'viewport');
metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
if (docEl.firstElementChild) {
docEl.firstElementChild.appendChild(metaEl);
} else {
var wrap = doc.createElement('div');
wrap.appendChild(metaEl);
doc.write(wrap.innerHTML);
}
}
function refreshRem(){
var width = docEl.getBoundingClientRect().width;
if (width / dpr > 540) {
width = 540 * dpr;
}
var rem = width / 10;
docEl.style.fontSize = rem + 'px';
flexible.rem = win.rem = rem;
}
win.addEventListener('resize', function() {
clearTimeout(tid);
tid = setTimeout(refreshRem, 300);
}, false);
win.addEventListener('pageshow', function(e) {
if (e.persisted) {
clearTimeout(tid);
tid = setTimeout(refreshRem, 300);
}
}, false);
if (doc.readyState === 'complete') {
doc.body.style.fontSize = 12 * dpr + 'px';
} else {
doc.addEventListener('DOMContentLoaded', function(e) {
doc.body.style.fontSize = 12 * dpr + 'px';
}, false);
}
refreshRem();
flexible.dpr = win.dpr = dpr;
flexible.refreshRem = refreshRem;
flexible.rem2px = function(d) {
var val = parseFloat(d) * this.rem;
if (typeof d === 'string' && d.match(/rem$/)) {
val += 'px';
}
return val;
}
flexible.px2rem = function(d) {
var val = parseFloat(d) / this.rem;
if (typeof d === 'string' && d.match(/px$/)) {
val += 'rem';
}
return val;
}
})(window, window['lib'] || (window['lib'] = {}));meta标签
<meta>标签有很多种，而这里要着重说的是viewport的meta标签，其主要用来告诉浏览器如何规范的渲染Web页面，而你则需要告诉它视窗有多大。在开发移动端页面，我们需要设置meta标签如下：
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">//如果你确定要用这个js请屏蔽掉，该js会自动创建js会在html标签内创建这个：
<html data-dpr="2" style="font-size: 64px;">现在样式写法
.test{background: url(img/m3-phone.32.png) no-repeat; background-size:122px 247px; width: 122px; height: 247px;}
[data-dpr="2"] .test {
background: url(img/m3-phone.32@2x.png) no-repeat;
}这段js是来自淘宝移动端自适应方案，
详细链接：http://www.cnblogs.com/lyzg/p/5058356.html
在github：https://github.com/amfe/lib-flexible
方法二：
第二个方法则是使用css的device-pixel-ratio具体的写法如下：
.test1-r {
background: url(img/m3-phone.32.png) no-repeat;
background-size: 122px 247px;
width: 122px;
height: 247px;
}
@media all and (-webkit-min-device-pixel-ratio: 1.5),
all and (-o-min-device-pixel-ratio: 3 / 2),
all and (min--moz-device-pixel-ratio: 1.5),
all and (min-device-pixel-ratio: 1.5) {
.test1-r {
background: url(img/m3-phone.32@2x.png) no-repeat;
background-size: 122px 247px;
}
}
@media (-webkit-min-device-pixel-ratio: 2),
(min-resolution: 192dpi) {
.test1-r {
background: url(img/m3-phone.32@2x.png) no-repeat;
background-size: 122px 247px;
}
}
@media (-webkit-min-device-pixel-ratio: 3),
(min-resolution: 288dpi) {
.test1-r {
background: url(img/m3-phone.32@3x.png) no-repeat;
background-size: 122px 247px;
}
}方法三：
使用retina.js，具体的使用方法没有研究