search
HomeWeb Front-endHTML Tutorialbackground-position percentage principle_html/css_WEB-ITnose

When I was helping others adjust their code today, I saw a style:

background-position: 50% 0;background-size: 100% auto;

Background-size: 100% auto, which means the background image width It is the element width * 100%, and the height is scaled proportionally. See css3 background for details.

For background-position, it is natural to think that the percentage is calculated based on the width of the parent element, but background-position is really not, it has its own set of principles. Detailed introduction below.

1. Equivalent writing methods

When reading various tutorials, there are the following equivalent writing methods:

  • top left, left top is equivalent to 0% 0%.
  • top, top center, center top is equivalent to 50% 0%.
  • right top, top right is equivalent to 100% 0%.
  • left, left center, center left is equivalent to 0% 50%.
  • center, center center is equivalent to 50% 50%.
  • right, right center, center right is equivalent to 100% 50%.
  • bottom left , left bottom is equivalent to 0% 100%.
  • bottom, bottom center, center bottom is equivalent to 50% 100%.
  • bottom right, right bottom is equivalent to 100% 100% .
  • So why are left and top equivalent to 0% 0%, and right bottom equivalent to 100% 100%?

    2. Background-position percentage calculation formula

    background-postion:x y;x:{容器(container)的宽度?背景图片的宽度}*x百分比,超出的部分隐藏。y:{容器(container)的高度?背景图片的高度}*y百分比,超出的部分隐藏。

    With this formula, it is easy to understand how to write 100%. After a little calculation, it is easy to understand the above various equivalents. The way to write it.

    3. Examples

    1. background-position: center center is equivalent to background-position: 50% 50% is equivalent to background-position:?px ?px

    Background is used in the example The picture is as follows [Size: 200px*200px]:

    The background image is centered in the container.

    <style type="text/css">.wrap{    width: 300px;    height: 300px;    border:1px solid green;    background-image: url(img/image.png);    background-repeat: no-repeat;/*    background-position: 50% 50%;*/    background-position: center center;}</style><div class="wrap"></div>

    The effect is to center the background image

    As above, the background image can be centered by setting the percentage and keywords. If you want to achieve How much should be set to center the image through specific values?

    According to the above formula:

    x=(width of container - background image width)*x percentage=(300px-200px)*50%=50px;

    y= (Container height - background image height) * y percentage = (300px - 200px) * 50% = 50px;

    That is, set background-postion: 50px 50px;

    Test it:

    <style type="text/css">.wrap{    width: 300px;    height: 300px;    border:1px solid green;    background-image: url(img/image.png);    background-repeat: no-repeat;/*    background-position: 50% 50%;*//*    background-position: center center;*/    background-position: 50px 50px;}</style><div class="wrap"></div>

    The effect is also centered.

    Statement
    The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
    Difficulty in updating caching of official account web pages: How to avoid the old cache affecting the user experience after version update?Difficulty in updating caching of official account web pages: How to avoid the old cache affecting the user experience after version update?Mar 04, 2025 pm 12:32 PM

    The official account web page update cache, this thing is simple and simple, and it is complicated enough to drink a pot of it. You worked hard to update the official account article, but the user still opened the old version. Who can bear the taste? In this article, let’s take a look at the twists and turns behind this and how to solve this problem gracefully. After reading it, you can easily deal with various caching problems, allowing your users to always experience the freshest content. Let’s talk about the basics first. To put it bluntly, in order to improve access speed, the browser or server stores some static resources (such as pictures, CSS, JS) or page content. Next time you access it, you can directly retrieve it from the cache without having to download it again, and it is naturally fast. But this thing is also a double-edged sword. The new version is online,

    How do I use HTML5 form validation attributes to validate user input?How do I use HTML5 form validation attributes to validate user input?Mar 17, 2025 pm 12:27 PM

    The article discusses using HTML5 form validation attributes like required, pattern, min, max, and length limits to validate user input directly in the browser.

    How to efficiently add stroke effects to PNG images on web pages?How to efficiently add stroke effects to PNG images on web pages?Mar 04, 2025 pm 02:39 PM

    This article demonstrates efficient PNG border addition to webpages using CSS. It argues that CSS offers superior performance compared to JavaScript or libraries, detailing how to adjust border width, style, and color for subtle or prominent effect

    What are the best practices for cross-browser compatibility in HTML5?What are the best practices for cross-browser compatibility in HTML5?Mar 17, 2025 pm 12:20 PM

    Article discusses best practices for ensuring HTML5 cross-browser compatibility, focusing on feature detection, progressive enhancement, and testing methods.

    What is the purpose of the <datalist> element?What is the purpose of the <datalist> element?Mar 21, 2025 pm 12:33 PM

    The article discusses the HTML <datalist> element, which enhances forms by providing autocomplete suggestions, improving user experience and reducing errors.Character count: 159

    What is the purpose of the <meter> element?What is the purpose of the <meter> element?Mar 21, 2025 pm 12:35 PM

    The article discusses the HTML <meter> element, used for displaying scalar or fractional values within a range, and its common applications in web development. It differentiates <meter> from <progress> and ex

    How do I use the HTML5 <time> element to represent dates and times semantically?How do I use the HTML5 <time> element to represent dates and times semantically?Mar 12, 2025 pm 04:05 PM

    This article explains the HTML5 <time> element for semantic date/time representation. It emphasizes the importance of the datetime attribute for machine readability (ISO 8601 format) alongside human-readable text, boosting accessibilit

    What is the purpose of the <progress> element?What is the purpose of the <progress> element?Mar 21, 2025 pm 12:34 PM

    The article discusses the HTML <progress> element, its purpose, styling, and differences from the <meter> element. The main focus is on using <progress> for task completion and <meter> for stati

    See all articles

    Hot AI Tools

    Undresser.AI Undress

    Undresser.AI Undress

    AI-powered app for creating realistic nude photos

    AI Clothes Remover

    AI Clothes Remover

    Online AI tool for removing clothes from photos.

    Undress AI Tool

    Undress AI Tool

    Undress images for free

    Clothoff.io

    Clothoff.io

    AI clothes remover

    AI Hentai Generator

    AI Hentai Generator

    Generate AI Hentai for free.

    Hot Article

    R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
    2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
    Repo: How To Revive Teammates
    1 months agoBy尊渡假赌尊渡假赌尊渡假赌
    Hello Kitty Island Adventure: How To Get Giant Seeds
    4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

    Hot Tools

    SAP NetWeaver Server Adapter for Eclipse

    SAP NetWeaver Server Adapter for Eclipse

    Integrate Eclipse with SAP NetWeaver application server.

    EditPlus Chinese cracked version

    EditPlus Chinese cracked version

    Small size, syntax highlighting, does not support code prompt function

    Dreamweaver Mac version

    Dreamweaver Mac version

    Visual web development tools

    Notepad++7.3.1

    Notepad++7.3.1

    Easy-to-use and free code editor

    VSCode Windows 64-bit Download

    VSCode Windows 64-bit Download

    A free and powerful IDE editor launched by Microsoft