html - 何时使用 IMG 与 CSS 背景图像？

Question

IMG在什么情况下使用 HTML标签来显示图像比 CSS更合适，background-image反之亦然？

因素可能包括可访问性、浏览器支持、动态内容或任何类型的技术限制或可用性原则。

score 879 · Accepted Answer

Proper uses of IMG

Use IMG if you intend to have people print your page and you want the image to be included by default. —JayTee
Use IMG (with alt text) when the image has an important semantic meaning, such as a warning icon. This ensures that the meaning of the image can be communicated in all user-agents, including screen readers.

Pragmatic uses of IMG

Use IMG plus alt attribute if the image is part of the content such as a logo or diagram or person (real person, not stock photo people). —sanchothefat
Use IMG if you rely on browser scaling to render an image in proportion to text size.
Use IMG for multiple overlay images in IE6.
~~Use IMG with a z-index in order to stretch a background image to fill its entire window.~~
Note, this is no longer true with CSS3 background-size; see #6 below.
Using img instead of background-image can dramatically improve performance of animations over a background.

When to use CSS background-image

Use CSS background images if the image is not part of the content. —sanchothefat
Use CSS background images when doing image-replacement of text eg. paragraphs/headers. —sanchothefat
Use background-image if you intend to have people print your page and you do not want the image to be included by default. —JayTee
Use background-image if you need to improve download times, as with CSS sprites.
Use background-image if you need for only a portion of the image to be visible, as with CSS sprites.
Use background-image with background-size:cover in order to stretch a background image to fill its entire window.

score 305 · Accepted Answer

对我来说，这是一个非黑即白的决定。如果图像是内容的一部分，例如徽标或图表或人物（真人，而不是照片人物），则使用<img />标签加 alt 属性。对于其他所有内容，都有 CSS 背景图像。

另一个使用 CSS 背景图像的时间是在对文本进行图像替换时，例如。段落/标题。

score 119 · Accepted Answer

I'm surprised no one's mentioned this yet: CSS transitions.

You can natively transition a div's background image:

#some_div {
    background-image:url(image_1.jpg);
    -webkit-transition:background-image 0.5s;
    /* Other vendor-prefixed transition properties */
    transition:background-image 0.5s;
}

#some_div:hover {
    background-image:url(image_2.jpg);
}

This saves any kind of JavaScript or jQuery animation to fade an <img/>'s src.

More information about transitions on MDN.

score 80 · Accepted Answer

Above answers considers only Design aspect . I am listing it in SEO aspects.

When to use <img />

When Your Image need to be indexed by search engine
If it has relation to content, including cards (click areas), but not related to design. Design is probably the most difficult thing to parse here because so it's all design right. I would say perhaps functional design (Cards, thumbnails, profile images, things you can click) vs Aesthetic design which is mostly used for sites appeal.
List item
If your image is not too small ( not iconic images ).
Images where you can add alt and title attribute.
Images from a webpage which you want to print using print media css

When to use CSS background-image

Images Purely Used to Design.
No Relation With Content.
Small Images which we can play with CSS3.
Repeating Images ( In blog author icon , date icon will be repeated for each article etc.,).

As i will use them based on these reasons. These are Good practices of Search Engine Optimization of Images.

score 56 · Accepted Answer

默认情况下，浏览器并不总是设置为打印背景图像；如果您打算让人们打印您的页面:)

score 53 · Accepted Answer

如果您将 CSS 保存在外部文件中，那么将站点中经常使用的图像（例如标题图像）显示为背景图像通常会很方便，因为这样您以后可以灵活地更改图像。

例如，假设您有以下 HTML：

<div id="headerImage"></div>

...和CSS：

#headerImage {
    width: 200px;
    height: 100px;
    background: url(Images/headerImage.png) no-repeat;
}

几天后，您更改了图像的位置。您所要做的就是更新 CSS：

#headerImage {
    width: 200px;
    height: 100px;
    background: url(../resources/images/headerImage.png) no-repeat;
}

Otherwise, you'd have to update the src attribute of the appropriate <img> tag in every HTML file (assuming you're not using a server-side scripting language or CMS to automate the process).

Also background images are useful if you don't want the user to be able to save the image (although I haven't ever needed to do this).

score 47 · Accepted Answer

About the same as sanchothefat's answer, but from a different aspect. I always ask myself: if I would completely remove the stylesheets from the website, do the remaining elements only belong to the content? If so, I did my job well.

score 45 · Accepted Answer

Some answers overcomplicate the scenario here. This is a dead simple situation.

Just answer to this question every time you'd like to place an image:

Is this part of the content or part of the design?

If you can't answer this, you probably don't know what you're doing or what you want to do!

Also, DO NOT consider beside the two technique, just because you'd wish to be "printer friendly" or not. Also DO NOT hide content from a SEO point of view with CSS. If you find yourself managing your content in CSS files, you shot yourself in the leg. This is just a trivial decision of what is content or not. Every other aspect should be ignored.

score 28 · Accepted Answer

I would add another two arguments:

An img tag is good if you need to resize the image. E.g. if the original image is 100px by 100 px, and you want it to be 80px by 80px, you can set the CSS width and height of the img tag. ~~I don't know of any good way to do this using background-image.~~ EDIT: This can now also be done with a background-image, using the background-size CSS3 attribute.
Using background-image is good when you need to dynamically switch between sprites. E.g. if you have a button image, and you want a separate image displayed when the cursor is hovering over the element, you can use a background image containing both the normal and hover sprites, and dynamically change the background-position.

score 23 · Accepted Answer

One more benefit from using the <IMG> tag is related to SEO - i.e. you can provide additional information about the image in the ALT attribute of the image tag, while there's no way to provide such information when specifying the image through CSS and in that case only the image file name may be indexed by search engines. The ALT attribute definitely gives the <IMG> tag SEO advantage over the CSS approach. That's why according to me it is better to specify the images you want to rank well in the image search results (e.g. Google Image Search) using the <IMG> tag.

score 19 · Accepted Answer

19

Foreground = img.

Background = CSS background.

于 2009-05-22T18:03:51.397 回答

score 14 · Accepted Answer

Use background images only when necessary e.g. containers with image that tiles.

One of the major PROS by using IMAGES is that it is better for SEO.

score 12 · Accepted Answer

Using a background image, you need to absolutely specify the dimensions. This can be a significant problem if you don't actually know them in advance or cannot determine them.

A big problem with <img /> is overlays. What if I want an CSS inner shadow on my image (box-shadow:inset 0 0 5px rgb(0,0,0,.5))? In this case, since <img /> can't have child elements, you need to use positioning and add empty elements which equates to useless markup.

In conclusion, it's quite situational.

score 11 · Accepted Answer

A couple of other scenarios where background-image should be used:

When you want the image to change when the mouse is hovered upon it.
~~When you want to add rounded corners to the image. If you use img, the image leaks out of the rounded corners.~~

score 10 · Accepted Answer

在多个皮肤或设计版本的情况下使用 CSS background-image。Javascript 可用于动态更改元素的类，这将迫使它呈现不同的图像。使用 IMG 标签，可能会更棘手。

score 7 · Accepted Answer

这是一个技术考虑：图像会动态生成吗？在 HTML中生成标签往往<img>比尝试动态编辑 CSS 属性容易得多。

score 7 · Accepted Answer

What about the size of the image? If I use the img tag, the browser scales the image. If I use css background, the browser just cuts a chunk from the larger image.

score 7 · Accepted Answer

In regards to animating images using CSS TranslateX/Y (The proper way to animate html) - If you do a Chrome Timeline recording of CSS background-images being animated vs IMG tags being animated you will see the paint times are drastically shorter for the CSS background-images.

score 7 · Accepted Answer

There's another reason! If you have a responsive design and want to split usage of low, medium, and high-res images for devices through media queries, you should use backgrounds as well.

score 6 · Accepted Answer

img is an html tag for a reason, therefore it should be used. For referencing or to illustrate things, people e.g: in articles.

Also if the image has a meaning or has to be clickable an img is better than a css background. For all other situation, I think, a css background can be used.

Although, it is a subject that needs to be discussed over and over.

Web Student from Paris, France

score 6 · Accepted Answer

Also, i have a gallery section which has inconsistent picture sizes so even though those images are obviously considered content, I use background images and center them in divs with a set size. This is similar to what facebook does in their albums..

score 5 · Accepted Answer

Just a small one to add, you should use the img tag if you want users to be able to 'right click' and 'save-image'/'save-picture', so if you intend to provide the image as a resource for others.

Using background image will (as far as I'm aware on most browsers) disable the option to save the image directly.

score 5 · Accepted Answer

A small input, I have had problems with responsive images slowing down the rendering on iphone for up to a minute, even with small images:

<!-- Was super slow -->
<div class="stuff">
    <img src=".." width="100%" />
</div>

But when switching to using background images the problem went away, this is only viable if targeting newer browsers.

score 4 · Accepted Answer

HTML is for content and CSS is for design. Is the image necessary and does it need to be picked up by screen readers? If the answer is yes, then put the image in the HTML. If it is purely for styling, then you can use the background-image property in CSS to inject the image. Just as a lot of people here have already mentioned, you can then use a pseudo element on the image if you like.

score 4 · Accepted Answer

IMG load first because the src is in the html file itself whereas in the case of background-image the source is mentioned in stylesheet so the image loads after the stylesheet loaded, delaying the loading of the webpage.

score 3 · Accepted Answer

Another background-image PRO: Background-images for <ul>/<ol> lists.

Use background images if they are part of the overall-design and are repeated on multiple pages. Preferably in background sprite form for optimization.

Use tags for all images that are not part of the overall design, and are most likely placed once, like specific images for articles, people, and important images that deserve to be added to google images.

** The only repeated image that I enclose in a <img> tag is the site/company logo. Because people tend to click it to go to the homepage, thus you wrap it with an <a> tag.

score 3 · Accepted Answer

Also note that most search engine spiders don't index CSS background images therefore the background images will be ignored and you won't be able to get any traffic from search engines (no SEO benefit in short).

Where as all images defined with tags are indexed (unless manually excluded) and can bring in traffic from search engines if their title/alt attributes and filenames are optimized properly (w.r.t some keyword).

score 2 · Accepted Answer

You can use IMG tags if you want the images to be fluid and scale to different screen sizes. For me these images are mostly part of the content. For most elements that are not part of the content, I use CSS sprites to keep the download size minimal unless I really want to animate icons etc.

score 2 · Accepted Answer

I use image instead of background-image when i want to make them 100% stretchable which supported in most browsers.

score 2 · Accepted Answer

If you want to add an image only for the special content on the page or for only one page the you should use IMG tag and if you want to put image on more than one pages then you should use CSS Background Image.

score 0 · Accepted Answer

Just to throw a spanner in the works - i'm of the opinion that you should never use the img tag. HTML was meant for content, not visual style. all the images on your page should come from the CSS, leaving your HTML code pure. (even if it does take a bit longer to build)

html - 何时使用 IMG 与 CSS 背景图像？

31 回答 31

Proper uses of IMG

Pragmatic uses of IMG

When to use CSS background-image

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