Unslider：即使在“低”屏幕分辨率下也能居中图像

Question

我在一个项目中使用 Unslider (http://unslider.com/)。

我成功地将整个滑块部分对齐到目标的一半。 但问题是1920 和更低宽度分辨率的幻灯片没有居中。图片的宽度为 3940 像素。

我尝试应用来自this 答案的代码；像这样：

$(function () {
  $('.banner').unslider();
  AdjustSliderImgWrapper();
});

$(window).resize(AdjustSliderImgWrapper);

function AdjustSliderImgWrapper() {
  var left = (parseInt($('.banner > li > img').width()) - $('.banner > li').innerWidth()) / -2;
  $('.banner > li > img').css('left', left);
}

，但无济于事。我也试过：

$(".banner img").each(function () {
    $(this).css("margin-left", -this.width / 2);
})

还有：

background-position: center center !important;

这是我的代码：

window.console && console.warn("This version of Unslider is due to be deprecated by December 1. Please visit unslider.com for details on how to upgrade."), function (t, s) {
	if (!t)
		return s;
	var i = function () {
		this.el = s,
		this.items = s,
		this.sizes = [],
		this.max = [0, 0],
		this.current = 0,
		this.interval = s,
		this.opts = {
			speed : 500,
			delay : 3e3,
			complete : s,
			keys : !s,
			dots : s,
			fluid : s
		};
		var i = this;
		this.init = function (s, i) {
			return this.el = s,
			this.ul = s.children("ul"),
			this.max = [s.outerWidth(), s.outerHeight()],
			this.items = this.ul.children("li").each(this.calculate),
			this.opts = t.extend(this.opts, i),
			this.setup(),
			this
		},
		this.calculate = function (s) {
			var e = t(this),
			n = e.outerWidth(),
			h = e.outerHeight();
			i.sizes[s] = [n, h],
			n > i.max[0] && (i.max[0] = n),
			h > i.max[1] && (i.max[1] = h)
		},
		this.setup = function () {
			if (this.el.css({
					overflow : "hidden",
					width : i.max[0],
					height : this.items.first().outerHeight()
				}), this.ul.css({
					width : 100 * this.items.length + "%",
					position : "relative"
				}), this.items.css("width", 100 / this.items.length + "%"), this.opts.delay !== s && (this.start(), this.el.hover(this.stop, this.start)), this.opts.keys && t(document).keydown(this.keys), this.opts.dots && this.dots(), this.opts.fluid) {
				var e = function () {
					i.el.css("width", Math.min(Math.round(i.el.outerWidth() / i.el.parent().outerWidth() * 100), 100) + "%")
				};
				e(),
				t(window).resize(e)
			}
			this.opts.arrows && this.el.parent().append('<p class="arrows"><span class="prev">â†</span><span class="next">→</span></p>').find(".arrows span").click(function () {
				t.isFunction(i[this.className]) && i[this.className]()
			}),
			t.event.swipe && this.el.on("swipeleft", i.prev).on("swiperight", i.next)
		},
		this.move = function (s, e) {
			this.items.eq(s).length || (s = 0),
			0 > s && (s = this.items.length - 1);
			var n = this.items.eq(s),
			h = {
				height : n.outerHeight()
			},
			o = e ? 5 : this.opts.speed;
			this.ul.is(":animated") || (i.el.find(".dot:eq(" + s + ")").addClass("active").siblings().removeClass("active"), this.el.animate(h, o) && this.ul.animate(t.extend({
						left : "-" + s + "00%"
					}, h), o, function () {
					i.current = s,
					t.isFunction(i.opts.complete) && !e && i.opts.complete(i.el)
				}))
		},
		this.start = function () {
			i.interval = setInterval(function () {
					i.move(i.current + 1)
				}, i.opts.delay)
		},
		this.stop = function () {
			return i.interval = clearInterval(i.interval),
			i
		},
		this.keys = function (s) {
			var e = s.which,
			n = {
				37 : i.prev,
				39 : i.next,
				27 : i.stop
			};
			t.isFunction(n[e]) && n[e]()
		},
		this.next = function () {
			return i.stop().move(i.current + 1)
		},
		this.prev = function () {
			return i.stop().move(i.current - 1)
		},
		this.dots = function () {
			var s = '<ol class="dots">';
			t.each(this.items, function (t) {
				s += '<li class="dot' + (1 > t ? " active" : "") + '">' + (t + 1) + "</li>"
			}),
			s += "</ol>",
			this.el.addClass("has-dots").append(s).find(".dot").click(function () {
				i.move(t(this).index())
			})
		}
	};
	t.fn.unslider = function (s) {
		var e = this.length;
		return this.each(function (n) {
			var h = t(this),
			o = (new i).init(h, s);
			h.data("unslider" + (e > 1 ? "-" + (n + 1) : ""), o)
		})
	}
}
(window.jQuery, !1);

* {
    margin: 0;
    padding: 0;
}
#outermin1 {
width : 100%;
}
.banner {
position : relative;
width : auto !important;
overflow : auto;
text-align : center;
}
/*
 */

.banner ul {
list-style : none;
width : 300%;
padding: 0px;
}
.banner ul li {
display : block;
float : left;
width : 33%;
padding : 0 0 110px;
min-height: 1550px !important;
max-height: 1550px !important;
}
.banner h1 {
position : relative;
margin : 0 auto;
height : 120px;
top : 30px;
text-align : center;
font-size : 250% !important ;
color : #FFF;
text-transform : uppercase;
font-weight : 100;
/*line-height : 38px !important ;*/
}
.banner h2 {
text-transform : none;
font-size : 150%;
top : -15px;
position : relative;
color : #FFF;
}
.banner .btn {
display : inline-block;
margin : 25px 0 0;
padding : 9px 22px 7px;
clear : both;
color : #fff;
font-size : 12px;
font-weight : 700;
text-transform : uppercase;
text-decoration : none;
border : rgba(255, 255, 255, 0.4) solid 2px;
border-radius : 5px;
}
.banner .btn:hover {
background : rgba(255, 255, 255, 0.05);
}
.banner .dots {
    position: absolute;
    left: 0px;
    right: 0px;
    bottom: -10px;
    background: #fff;
    height: 103px;
    padding-top: 30px;
}
.banner .dots li {
display : inline-block;
width : 10px;
height : 10px;
margin : 0 4px;
text-indent : -999em;
border : #17b7a5 solid 2px;
border-radius : 6px;
cursor : pointer;
opacity : 0.4000000059604644775390625;
transition : background 0.5s, opacity 0.5s;
}
.banner .dots li.active {
background : #17b7a5;
opacity : 1;
}
/*
.banner img {
    width: 100%;
    margin-top: -143px;
}*/
.banner img {
    background-size: cover;
    z-index: 3;
} 
/* this  is the tryout part */
.banner > li { position: relative; }
.banner > li > img { position: absolute; top: 0; width: 3940px !important; text-align: center;}

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->
    <meta name="description" content="">
    <meta name="author" content="">
    <link rel="icon" href="favicon.ico">

    <title>theimapcter.org</title>

    <!-- Bootstrap core CSS -->
    <link href="css/bootstrap.min.css" rel="stylesheet">
    <!-- IE10 viewport hack for Surface/desktop Windows 8 bug -->
    <link href="css/ie10-viewport-bug-workaround.css" rel="stylesheet">

    <!-- Custom styles for this template -->
    <link href="css/banner.css" rel="stylesheet">
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    <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
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    <![endif]-->
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script src="js/unslider.min.js"></script>
	    <script type="text/javascript">
$(function() {
    $('.banner').unslider({
    speed: 500,               
    delay: 15000,              
    complete: function() {},  
    keys: true,               
    dots: true,               
    fluid: true              
    });
});

</script>
  </head>

  <body>

    <nav class="navbar navbar-inverse navbar-fixed-top">
        <div class="navbar-header">
          <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
            <span class="sr-only">Toggle navigation</span>
            <span class="icon-bar"></span>
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          </button>
 		<a class="navbar-brand" href="#"><img src="svg/impacter_logo_fejlec.svg" alt="logo"></a>         
        </div>
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        <ul class="nav navbar-nav">
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		</li>
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		<h1>Develop new ways to solve actual social / environmental challenges</h1><br/><br/><h2><strong class="line2">– meanwhile learn about yourself.</strong></h2><span>Challenges</span><span>Taking<br/>the responsibility</span><span>Response</span><span>Make an impact</span></div></div><img src="https://dl.dropboxusercontent.com/s/geiezcd6hym6mxt/slide3.png" alt="people on pc" class="slide3" /></div></li>
    </ul>
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</div>

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</html>

编辑 2016.07.23.: 我忘了提到，我只想将图像的 1920px 部分居中。

Answer 1

解决方案是：将图像包装在 parent 类中，并为图像添加 child 类，

<span class="parent"><img class="child"...>

并给他们居中，像这样：

.parent {
    position: relative;
    overflow: hidden;
}

.child {
    position: absolute;
    left: -9999px;
    right: -9999px;
    margin: auto;
}

然后在.banner ul li 上添加一个overflow:hidden;，以便div 不会相互重叠。

Answer 2

我更喜欢另一个技巧。我不知道您的特定滑块是否可以为 div 设置动画，但您可以将图像作为背景图像提供给该 div。而不是使用background-size: cover;，浏览器将始终为您选择合适的尺寸。