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How to adapt css background image

anonymityOriginal: 2019-05-28 15:06:488483browse

A clear and beautiful background picture can add a lot of points to a web page. Designers often use large pictures for the background of the page. We neither want the picture to be deformed due to different resolutions, nor do we want it to be displayed on a large screen. In this case, there is a white patch in the background. In short, it is to realize a large background image that can adapt to the screen size without deforming, and the background image will not scroll as the scroll bar scrolls, so that the background image can be adapted.

Here’s how to do it with CSS:

HTML:

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="content-type" content="text/html;charset=utf-8"/>
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <title>title</title>
</head>
<body>
<div class="wrapper">
    <!--背景图片-->
    <div id="web_bg" style="background-image: url(./img/bg.jpg);"></div>
    <!--其他代码 ... -->
</div>
</body>
</html>

CSS:

#web_bg{
  position:fixed;
  top: 0;
  left: 0;
  width:100%;
  height:100%;
  min-width: 1000px;
  z-index:-10;
  zoom: 1;
  background-color: #fff;
  background-repeat: no-repeat;
  background-size: cover;
  -webkit-background-size: cover;
  -o-background-size: cover;
  background-position: center 0;
}

Next, let’s analyze the function of each code in css:

 position:fixed;  top: 0;  left: 0;

These three sentences make the entire div fixed at the top and left of the screen

 width:100%;  height:100%;  min-width: 1000px;

The first two sentences above are to make the entire div have the same size as the screen, so as to achieve the full-screen effect, and min-width is to keep the size of the div unchanged when the screen width is within 1000px, which means that in this case Next, when scaling the screen width, the image does not scale (only valid within 1000px).

 z-index:-10;

The purpose of this is to make the entire div below each level in the HTML page. Under normal circumstances, the z-index value of the first created level is 0, so if we write -1 here, it is okay. Implementation, but writing -10 here is to ensure that the entire div is at the bottom, because if there are too many levels in the page, sometimes -1 is not necessarily at the bottom, but it does not make sense if it is written as a large number like -100. Use index:-10 to achieve what looks like a background image. It is actually the most common div, but the hierarchical relationship has changed to make it look like a background image.

 background-repeat: no-repeat;

The above is the background, don’t repeat it

 background-size: cover;
  -webkit-background-size: cover;
  -o-background-size: cover;

The above three sentences have the same meaning, which is to make the picture scale synchronously with the screen size, but some parts may be cropped, but it will not be exposed. , the following two sentences are for compatibility with chrome and opera browsers.

 background-position: center 0;

The above sentence means the position of the picture, centered and aligned to the left.

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