如何解决移动端Retina屏1px像素的问题？
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参考技术A 首先我们先聊下Retina屏的概念。
Retina: 一种新型高分辨率的显示标准,又称视网膜显示屏。
在移动端开发中，UI设计稿中设置边框为1px，前端在开发中如果出现border:1px,测试会发现在Retina屏机型中，1px会比较粗，即是经典的移动端1px像素问题。
比如iphone6的屏幕宽度为375px，设计师的视觉稿一般是750px，如果UI的border 1px,而前端实际开发的时候是不能采用1px border的，应该是1px/2。
参考高级前端进阶
移动端 Retina屏 各大主流网站1px的解决方案
Retina屏的移动设备如何实现真正1px的线？
在retina屏下面，如果你写了这样的meta <meta name="viewport" content="initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
你将永远无法写出1px宽度的东西，除此之外，inline的SVG等元素，也会按照逻辑像素来渲染，整个页面的清晰度会打折；
先看看 “诸子百家 ” 是如何实现的；
先看看百度糯米的
@media only screen and (-webkit-min-device-pixel-ratio:2),only screen and (min-device-pixel-ratio:2) {
.normal-goods .good-content {
border: none;
background-image: -webkit-linear-gradient(90deg,#e0e0e0,#e0e0e0 50%,transparent 50%);
background-image: -moz-linear-gradient(90deg,#e0e0e0,#e0e0e0 50%,transparent 50%);
background-image: -o-linear-gradient(90deg,#e0e0e0,#e0e0e0 50%,transparent 50%);
background-image: linear-gradient(0,#e0e0e0,#e0e0e0 50%,transparent 50%);
background-size: 100% 1px;
background-repeat: no-repeat;
background-position: bottom
}
}
再看看 大众点评的
.index-rec .home-tuan-list .cnt {
padding: 7px 10px 10px 0;
display: box;
display: -webkit-box;
display: -ms-flexbox;
height: 78px;
background-image: url(//www.dpfile.com/mod/app-m-style/1.7.2/css/img/repeat-x.png);
background-repeat: repeat-x;
background-position: 0 bottom;
background-size: auto 1px
}
再看再看看 阿里去啊 ,其中 hairlines挂到 <html class=‘hairlines‘上>
<script>
if (/iP(hone|od|ad)/.test(navigator.userAgent)) { // 就是放到html根节点上的 ios8现在普及率高了，可以省略
var v = (navigator.appVersion).match(/OS (\d+)_(\d+)_?(\d+)?/), version = parseInt(
v[1], 10);
if (version >= 8) {
document.documentElement.classList.add(‘hairlines‘)
}
};
</script>
.r1bt {
border-top: 1px solid rgba(32,35,37,.15)
}
.r1bb {
border-bottom: 1px solid rgba(32,35,37,.15)
}
.r1bl {
border-left: 1px solid rgba(32,35,37,.15)
}
.r1br {
border-right: 1px solid rgba(32,35,37,.15)
}
.r1b {
border: 1px solid rgba(32,35,37,.15)
}
.hairlines .r1bt,.hairlines .r1bb,.hairlines .r1bl,.hairlines .r1br,.hairlines .r1b {
border-width: .5px!important
}
早期阿里去啊不是这样的 ，是这样写的，兼容性非常好
/*retain 1px border start*/
.retainbt,.retainbb,.retainbl,.retainbr,.retainb { position: relative;position: relative !important}
.retainbt:before,.retainbb:after {pointer-events: none;position: absolute;content: ""; height: 1px; background: rgba(32,35,37,.24);left: 0;right: 0}
.retainbt:before {top: 0}
.retainbb:after {bottom: 0}
.retainbl:before,.retainbr:after {pointer-events: none;position: absolute;content: ""; width: 1px; background: rgba(32,35,37,.24); top: 0; bottom: 0}
.retainbl:before {left: 0}
.retainbr:after {right: 0}
.retainb:after {position: absolute;content: "";top: 0;left: 0; -webkit-box-sizing: border-box; box-sizing: border-box; width: 100%; height: 100%; border: 1px solid rgba(32,35,37,.24); pointer-events: none}
@media (-webkit-min-device-pixel-ratio:1.5),(min-device-pixel-ratio:1.5),(min-resolution: 144dpi),(min-resolution:1.5dppx) {
.retainbt:before,.retainbb:after {-webkit-transform:scaleY(.5);transform: scaleY(.5) }
.retainbl:before,.retainbr:after {-webkit-transform: scaleX(.5); transform: scaleX(.5) }
.retainb:after { width: 200%; height: 200%;-webkit-transform: scale(.5); transform: scale(.5) }
.retainbt:before,.retainbl:before,.retainb:after {-webkit-transform-origin: 0 0;transform-origin: 0 0}
.retainbb:after,.retainbr:after { -webkit-transform-origin: 100% 100%;transform-origin: 100% 100%}
}
@media (-webkit-device-pixel-ratio:1.5) {
.retainbt:before,.retainbb:after { -webkit-transform: scaleY(.6666); transform: scaleY(.6666) }
.retainbl:before,.retainbr:after {-webkit-transform: scaleX(.6666); transform: scaleX(.6666)}
.retainb:after {width: 150%; height: 150%;-webkit-transform: scale(.6666); transform: scale(.6666) }
}
@media (-webkit-device-pixel-ratio:3) {
.retainbt:before,.retainbb:after { -webkit-transform: scaleY(.3333); transform: scaleY(.3333)}
.retainbl:before,.retainbr:after { -webkit-transform: scaleX(.3333); transform: scaleX(.3333)}
.retainb:after {width: 300%;height: 300%; -webkit-transform: scale(.3333);transform: scale(.3333)}
}
然后 再看看rem的解决方案
美团的
<script type="text/javascript">
//根据屏幕大小及dpi调整缩放和大小
(function() {
var scale = 1.0;
var ratio = 1;
if (window.devicePixelRatio >= 2) {
scale *= 0.5;
ratio *= 2;
}
var text = ‘<meta name="viewport" content="initial-scale=‘ + scale + ‘, maximum-scale=‘ + scale +‘, minimum-scale=‘ + scale + ‘, width=device-width, user-scalable=no" />‘;
document.write(text);
document.documentElement.style.fontSize = 50*ratio + "px";
})();
</script>
我们把美团的 改变一下也可以
美团的 改变一下
<meta name="viewport" content="target-densitydpi=device-dpi"> <!--安卓自带的 device-width 先不加 否则iphone 随进线条出现问题 -->
<script>
+function(win,doc,undefined) {//根据屏幕大小及dpi调整缩放和大小
var scale = 1.0,ratio = 1,dc=doc,viewporttexts=‘‘;
if (win.devicePixelRatio && devicePixelRatio >= 1.5) {
ratio = devicePixelRatio;
scale = scale/(devicePixelRatio);
}
//var texts = ‘<meta name="viewport" content="initial-scale=‘ + scale + ‘, maximum-scale=‘ + scale +‘, minimum-scale=‘ + scale + ‘, width=device-width, user-scalable=no" />‘;
// dc.write(texts);
viewporttexts = ‘ width=device-width, initial-scale=‘ + scale + ‘, maximum-scale=‘ + scale +‘, minimum-scale=‘ + scale + ‘,user-scalable=no‘;
doc.querySelector(‘meta[name="viewport"]‘).setAttribute("content",viewporttexts);
console.log(‘111‘);
dc.documentElement.style.fontSize =doc.getElementsByTagName("html")[0].style.fontSize=Math.ceil(50*ratio) + "px";
}(window,document);
</script>
最后淘宝的 这段代码有点旧了 https://github.com/amfe/lib-flexible
<script>
!function(N, M) {
function L() {
var a = I.getBoundingClientRect().width;
a / F > 540 && (a = 540 * F);
var d = a / 10;
I.style.fontSize = d + "px",
D.rem = N.rem = d
}
var K, J = N.document, I = J.documentElement, H = J.querySelector(‘meta[name="viewport"]‘), G = J.querySelector(‘meta[name="flexible"]‘), F = 0, E = 0, D = M.flexible || (M.flexible = {});
if (H) {
console.warn("将根据已有的meta标签来设置缩放比例");
var C = H.getAttribute("content").match(/initial\-scale=([\d\.]+)/);
C && (E = parseFloat(C[1]),
F = parseInt(1 / E))
} else {
if (G) {
var B = G.getAttribute("content");
if (B) {
var A = B.match(/initial\-dpr=([\d\.]+)/)
, z = B.match(/maximum\-dpr=([\d\.]+)/);
A && (F = parseFloat(A[1]),
E = parseFloat((1 / F).toFixed(2))),
z && (F = parseFloat(z[1]),
E = parseFloat((1 / F).toFixed(2)))
}
}
}
if (!F && !E) {
var y = N.navigator.userAgent
, x = (!!y.match(/android/gi),
!!y.match(/iphone/gi))
, w = x && !!y.match(/OS 9_3/)
, v = N.devicePixelRatio;
F = x && !w ? v >= 3 && (!F || F >= 3) ? 3 : v >= 2 && (!F || F >= 2) ? 2 : 1 : 1,
E = 1 / F
}
if (I.setAttribute("data-dpr", F),
!H) {
if (H = J.createElement("meta"),
H.setAttribute("name", "viewport"),
H.setAttribute("content", "initial-scale=" + E + ", maximum-scale=" + E + ", minimum-scale=" + E + ", user-scalable=no"),
I.firstElementChild) {
I.firstElementChild.appendChild(H)
} else {
var u = J.createElement("div");
u.appendChild(H),
J.write(u.innerHTML)
}
}
N.addEventListener("resize", function() {
clearTimeout(K),
K = setTimeout(L, 300)
}, !1),
N.addEventListener("pageshow", function(b) {
b.persisted && (clearTimeout(K),
K = setTimeout(L, 300))
}, !1),
"complete" === J.readyState ? J.body.style.fontSize = 12 * F + "px" : J.addEventListener("DOMContentLoaded", function() {
J.body.style.fontSize = 12 * F + "px"
}, !1),
L(),
D.dpr = N.dpr = F,
D.refreshRem = L,
D.rem2px = function(d) {
var c = parseFloat(d) * this.rem;
return "string" == typeof d && d.match(/rem$/) && (c += "px"),
c
}
,
D.px2rem = function(d) {
var c = parseFloat(d) / this.rem;
return "string" == typeof d && d.match(/px$/) && (c += "rem"),
c
}
}(window, window.lib || (window.lib = {}));
</script>
用rem写1px 维护行方便；
缺点：但是 动态控制 viewport retain下，无论美团还是淘宝用 rem始终还有许多细小的问题；在ios上浏览器打开仔细看还是看的出的，安卓上没看出来；
有时候retain下， viewport 缩放动态控制字体大小；<meta name="viewport" content="initial-scale=0.5, maximum-scale=0.5, minimum-scale=0.5, user-scalable=no"> 竖线或者奇数偶数行横线 视窗控制之后的1px线条，有的1.1px 或者1.2px等等...拿手机仔细看下，观察iphone5 以及iphone6 下就知道，但是截图出来也看不出来问题的（只是示范一下），真机上细看还是明显的；
美团KTV 全城 默认排序 刷选的 分割线 ；iphone5s 刷选的那条是正常的鹅；前面3条1px多了点；ip6上则不是；
上面 有的 竖线始终 感觉 宽度是 不是1px;宽了一点点；首页美食类目进去；每个店铺边框 偶尔几条线条是1px多了一点点；
喜欢那种就用那种好了；
顺便附个H5 Canvas Retina屏幕处理的1px的函数
/**
* HiDPI Canvas Polyfill (1.0.9)
*
* Author: Jonathan D. Johnson (http://jondavidjohn.com)
* Homepage: https://github.com/jondavidjohn/hidpi-canvas-polyfill
* Issue Tracker: https://github.com/jondavidjohn/hidpi-canvas-polyfill/issues
* License: Apache 2.0
*/
;(function(prototype) {
var pixelRatio = (function(context) {
var backingStore = context.backingStorePixelRatio ||
context.webkitBackingStorePixelRatio ||
context.mozBackingStorePixelRatio ||
context.msBackingStorePixelRatio ||
context.oBackingStorePixelRatio ||
context.backingStorePixelRatio || 1;
return (window.devicePixelRatio || 1) / backingStore;
})(prototype),
forEach = function(obj, func) {
for (var p in obj) {
if (obj.hasOwnProperty(p)) {
func(obj[p], p);
}
}
},
ratioArgs = {
‘fillRect‘: ‘all‘,
‘clearRect‘: ‘all‘,
‘strokeRect‘: ‘all‘,
‘moveTo‘: ‘all‘,
‘lineTo‘: ‘all‘,
‘arc‘: [0,1,2],
‘arcTo‘: ‘all‘,
‘bezierCurveTo‘: ‘all‘,
‘isPointinPath‘: ‘all‘,
‘isPointinStroke‘: ‘all‘,
‘quadraticCurveTo‘: ‘all‘,
‘rect‘: ‘all‘,
‘translate‘: ‘all‘,
‘createRadialGradient‘: ‘all‘,
‘createLinearGradient‘: ‘all‘
};
if (pixelRatio === 1) return;
forEach(ratioArgs, function(value, key) {
prototype[key] = (function(_super) {
return function() {
var i, len,
args = Array.prototype.slice.call(arguments);
if (value === ‘all‘) {
args = args.map(function(a) {
return a * pixelRatio;
});
}
else if (Array.isArray(value)) {
for (i = 0, len = value.length; i < len; i++) {
args[value[i]] *= pixelRatio;
}
}
return _super.apply(this, args);
};
})(prototype[key]);
});
// Stroke lineWidth adjustment
prototype.stroke = (function(_super) {
return function() {
this.lineWidth *= pixelRatio;
_super.apply(this, arguments);
this.lineWidth /= pixelRatio;
};
})(prototype.stroke);
// Text
//
prototype.fillText = (function(_super) {
return function() {
var args = Array.prototype.slice.call(arguments);
args[1] *= pixelRatio; // x
args[2] *= pixelRatio; // y
this.font = this.font.replace(
/(\d+)(px|em|rem|pt)/g,
function(w, m, u) {
return (m * pixelRatio) + u;
}
);
_super.apply(this, args);
this.font = this.font.replace(
/(\d+)(px|em|rem|pt)/g,
function(w, m, u) {
return (m / pixelRatio) + u;
}
);
};
})(prototype.fillText);
prototype.strokeText = (function(_super) {
return function() {
var args = Array.prototype.slice.call(arguments);
args[1] *= pixelRatio; // x
args[2] *= pixelRatio; // y
this.font = this.font.replace(
/(\d+)(px|em|rem|pt)/g,
function(w, m, u) {
return (m * pixelRatio) + u;
}
);
_super.apply(this, args);
this.font = this.font.replace(
/(\d+)(px|em|rem|pt)/g,
function(w, m, u) {
return (m / pixelRatio) + u;
}
);
};
})(prototype.strokeText);
})(CanvasRenderingContext2D.prototype);
;(function(prototype) {
prototype.getContext = (function(_super) {
return function(type) {
var backingStore, ratio,
context = _super.call(this, type);
if (type === ‘2d‘) {
backingStore = context.backingStorePixelRatio ||
context.webkitBackingStorePixelRatio ||
context.mozBackingStorePixelRatio ||
context.msBackingStorePixelRatio ||
context.oBackingStorePixelRatio ||
context.backingStorePixelRatio || 1;
ratio = (window.devicePixelRatio || 1) / backingStore;
if (ratio > 1) {
this.style.height = this.height + ‘px‘;
this.style.width = this.width + ‘px‘;
this.width *= ratio;
this.height *= ratio;
}
}
return context;
};
})(prototype.getContext);
})(HTMLCanvasElement.prototype);
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