垂直对齐div中的图像与响应高度 [英] Vertically align an image inside a div with responsive height

问题描述

我有以下代码，用于设置一个容器，当浏览器调整大小时，其高度随宽度而变化（保持正方形的宽高比）。

HTML

 < div class =responsive-container> 
< div class =dummy>< / div> 
< div class =img-container> 
< IMG HERE> 
< / div> 
< / div> 
  

CSS

  .responsive-container {
 position：relative; 
 width：100％; 
 border：1px solid black; 
} 
 
 .dummy {
 padding-top：100％; / * force 1：1 aspect ratio * / 
} 
 
 .img-container {
 position：absolute; 
 top：0; 
 bottom：0; 
 left：0; 
 right：0; 
} 
  

如何在容器中垂直对齐IMG？所有我的图像都有可变的高度，容器不能有固定的高度/行高，因为它响应...请帮助！

解决方案

以下是一种技术，可以同时水平和垂直对齐在父元素内的内联元素：

垂直对齐

1）在这种方法中，我们创建一个 inline-block 的第一个（或最后一个）子项，并将其 height 属性设置为 100％



2）此外，添加 vertical-align：middle 将行内（-block）元素保留在行空格的中间。因此，我们将CSS声明添加到第一个子和元素（图片）。

3）最后，为了删除 inline（-block）元素之间的空白字符，我们可以设置<

注意： 我在下面使用了Nicolas Gallagher的 百分比值

例如：

  .responsive-container {
 width：60％; 
 
 padding-top：60％; / * 1：1高度与宽度相同* / 
 padding-top：100％; / * width：height = 60：100或3：5 * / 
 padding-top：45％; / * = 60％* 3/4，width：height = 4：3 * / 
 padding-top：33.75％; / * = 60％* 9/16，width：height = 16：9 * / 
} 
  

以下是 在线演示 。

此外，我们可以应用 padding 属性到 dummy 子元素或：before / ：after 相同的结果。但是注意在这种情况下， padding 的百分比值相对于<$ c $的宽度 c> .responsive-container 本身。

 < div class =responsive-container> 
< div class =dummy>< / div> 
< / div> 
  

  .responsive-container {宽度：60％; } 
 
 .responsive-container .dummy {
 padding-top：100％; / * 1：1 square * / 
 padding-top：75％; / * w：h = 4：3 * / 
 padding-top：56.25％; / * w：h = 16：9 * / 
} 
  

Demo＃1 。

演示＃2 （：之后 pseudo-element）

添加内容

使用 padding-top 属性会在顶部产生巨大的空间底部的内容，在容器内。

为了解决这个问题，我们用wrapper元素包装内容，从文档正常流程中使用绝对定位，最后展开包装器（bu使用 top ， right ， bottom left 属性）来填充其父项容器的整个空间。

我们去：

  .responsive-container {
 width：60％; 
 position：relative; 
} 
 
 .responsive-container .wrapper {
 position：absolute; 
 top：0; right：0; bottom：0; left：0; 
} 
  

这里是 在线演示 。

---

整合

 < div class =responsive-container> 
< div class =dummy>< / div> 
 
< div class =img-container> 
< img src =http://placehold.it/150x150alt => 
< / div> 
< / div> 
  

  .img-container { 
 text-align：center; / *对齐中心内联元素* / 
 font：0/0 a; / *隐藏空格之类的字符* / 
} 
 
 .img-container：before {
 content：''; 
 display：inline-block; 
 vertical-align：middle; 
 height：100％; 
} 
 
 .img-container img {
 vertical-align：middle; 
 display：inline-block; 
} 
  

这里是 WORKING DEMO

。

显然，你可以避免使用 :: before 伪元素浏览器兼容性，并创建一个元素作为 .img-container ：

 < div class =img-container> 
< div class =centerer>< / div> 
< img src =http://placehold.it/150x150alt => 
< / div> 
  

  .img-container。 centerer {
 display：inline-block; 
 vertical-align：middle; 
 height：100％; 
} 
  

UPDATED DEMO 。

使用 max- *

为了保持图像在宽度较低的框中，您可以设置 max-height 和 max-width 属性：

  .img-container img {
 vertical-align：middle; 
 display：inline-block; 
 max-height：100％; / * < - 将最大高度设置为其父级的100％* / 
 max-width：100％; / * < - 将最大宽度设置为其父级的100％* / 
} 
  

这里是 更新的演示 。

I have the following code which sets up a container which has a height that changes with the width when the browser is re-sized (to maintain a square aspect ratio).

HTML

<div class="responsive-container">
    <div class="dummy"></div>
    <div class="img-container">
        <IMG HERE>
    </div>
</div>

CSS

.responsive-container {
    position: relative;
    width: 100%;
    border: 1px solid black;
}

.dummy {
    padding-top: 100%; /* forces 1:1 aspect ratio */
}

.img-container {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}

How can I vertically align the IMG inside the container? All my images have variable heights and the container can't have a fixed height/line height because it's responsive... Please help!

解决方案

Here is a technique to align inline elements inside a parent, horizontally and vertically at the same time:

Vertical Alignment

1) In this approach, we create an inline-block (pseudo-)element as the first (or last) child of the parent, and set its height property to 100% to take all the height of its parent.

2) Also, adding vertical-align: middle keeps the inline(-block) elements at the middle of the line space. So, we add that CSS declaration to the first-child and our element (the image) both.

3) Finally, in order to remove the white space character between inline(-block) elements, we could set the font size of the parent to zero by font-size: 0;.

Note: I used Nicolas Gallagher's image replacement technique in the following.

What are the benefits?

• The container (parent) can have dynamic dimensions.

• There's no need to specify the dimensions of the image element explicitly.

• We can easily use this approach to align a <div> element vertically as well; which may have a dynamic content (height and/or width). But note that you have to re-set the font-size property of the div to display the inside text. Online Demo.

<div class="container">
    <div id="element"> ... </div>
</div>

.container {
    height: 300px;
    text-align: center;  /* align the inline(-block) elements horizontally */
    font: 0/0 a;         /* remove the gap between inline(-block) elements */
}

.container:before {    /* create a full-height inline block pseudo=element */
    content: ' ';
    display: inline-block;
    vertical-align: middle;  /* vertical alignment of the inline element */
    height: 100%;
}

#element {
    display: inline-block;
    vertical-align: middle;  /* vertical alignment of the inline element */
    font: 16px/1 Arial sans-serif;        /* <-- reset the font property */
}

The output

Responsive Container

This section is not going to answer the question as the OP already knows how to create a responsive container. However, I'll explain how it works.

In order to make the height of a container element changes with its width (respecting the aspect ratio), we could use a percentage value for top/bottom padding property.

A percentage value on top/bottom padding or margins is relative to the width of the containing block.

For instance:

.responsive-container {
  width: 60%;

  padding-top: 60%;    /* 1:1 Height is the same as the width */
  padding-top: 100%;   /* width:height = 60:100 or 3:5        */
  padding-top: 45%;    /* = 60% * 3/4 , width:height =  4:3   */
  padding-top: 33.75%; /* = 60% * 9/16, width:height = 16:9   */
}

Here is the Online Demo. Comment out the lines from the bottom and resize the panel to see the effect.

Also, we could apply the padding property to a dummy child or :before/:after pseudo-element to achieve the same result. But note that in this case, the percentage value on padding is relative to the width of the .responsive-container itself.

<div class="responsive-container">
  <div class="dummy"></div>
</div>

.responsive-container { width: 60%; }

.responsive-container .dummy {
  padding-top: 100%;    /*  1:1 square */
  padding-top: 75%;     /*  w:h =  4:3 */
  padding-top: 56.25%;  /*  w:h = 16:9 */
}

Demo #1.
Demo #2 (Using :after pseudo-element)

Adding the content

Using padding-top property causes a huge space at the top or bottom of the content, inside the container.

In order to fix that, we have wrap the content by a wrapper element, remove that element from document normal flow by using absolute positioning, and finally expand the wrapper (bu using top, right, bottom and left properties) to fill the entire space of its parent, the container.

Here we go:

.responsive-container {
  width: 60%;
  position: relative;
}

.responsive-container .wrapper {
  position: absolute;
  top: 0; right: 0; bottom: 0; left: 0;
}

Here is the Online Demo.

---

Getting all together

<div class="responsive-container">
  <div class="dummy"></div>

  <div class="img-container">
    <img src="http://placehold.it/150x150" alt="">
  </div>
</div>

.img-container {
  text-align:center; /* Align center inline elements */
  font: 0/0 a;       /* Hide the characters like spaces */
}

.img-container:before {
  content: ' ';
  display: inline-block;
  vertical-align: middle;
  height: 100%;
}

.img-container img {
  vertical-align: middle;
  display: inline-block;
}

Here is the WORKING DEMO.

Obviously, you could avoid using ::before pseudo-element for browser compatibility, and create an element as the first child of the .img-container:

<div class="img-container">
    <div class="centerer"></div>
    <img src="http://placehold.it/150x150" alt="">
</div>

.img-container .centerer {
  display: inline-block;
  vertical-align: middle;
  height: 100%;
}

UPDATED DEMO.

Using max-* properties

In order to keep the image inside of the box in lower width, you could set max-height and max-width property on the image:

.img-container img {
    vertical-align: middle;
    display: inline-block;
    max-height: 100%;  /* <-- Set maximum height to 100% of its parent */
    max-width: 100%;   /* <-- Set maximum width to 100% of its parent */
}

Here is the UPDATED DEMO.

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