To add multiple background images to web page elements, CSS supports comma-separated implementation. The specific methods are: 1. Use commas to separate multiple image paths in the background-image attribute, such as url('top-pattern.png'), url('main-bg.jpg'); 2. Pay attention to the order, the first image is displayed on the top layer; 3. You can set the display method of each image with background-repeat, background-position and other attributes, and keep the order one by one; 4. Common combinations include controlling repetition, position, size and blending mode; 5. Pay attention to compatibility (not supported by IE8 and earlier versions), performance (avoid too large images) and hierarchical order issues; 6. Abbreviation attributes may cause all images to inherit the same value, and it is recommended to write them separately for clearer. After mastering these key points, the implementation of multi-background images will be more flexible and reliable.

Sometimes we want to add multiple background images to a web page element, such as displaying a main image and a decorative pattern on the same div at the same time. CSS actually supports this operation, but the writing method is a bit special.

Separate multiple background images with commas

This is the most core method: use commas in background-image property , separate multiple image paths. This way the browser will stack them layer by layer.

 .element {
  background-image: url('top-pattern.png'), url('main-bg.jpg');
}

Note the order: The first picture will be covered on the top and the ones in the back will be arranged downwards in sequence. This is very important. If you find that a certain picture is not displayed, it may be covered.

It can also be set with other background properties, such as:

 background-repeat: repeat, no-repeat;
background-position: top left, center;

It should also be separated by commas, and the order should be one by one.

Commonly used attribute combinations when setting multiple backgrounds

In addition to background-image , there are several properties that are often used together:

• background-repeat : Controls whether each image is repeated
• background-position : Set the position of each image
• background-size : You can set the size separately for each image
• background-blend-mode : layer blending mode (advanced usage)

For example:

 background-image: url('overlay.png'), url('bg.jpg');
background-repeat: no-repeat, repeat;
background-position: center, top left;
background-size: cover, auto;

This allows the overlay image to be centered over the background image.

Notes and FAQs

Although multi-background images are powerful, there are several errors that are prone to errors:

• Compatibility is OK : mainstream browsers support it, but if you still have to take care of IE8 or earlier, you have to find another way.
• Performance considerations : Adding too many pictures will affect the loading speed, especially large pictures or high-definition pictures. It is recommended to control the number.
• Don’t reverse the hierarchy order : As mentioned earlier, the first one is written on the top layer, and if the order is incorrect, the effect will not be seen.
• Be careful with abbreviation properties : If you use background abbreviation properties, all graphs will inherit the same repeat/position values, so it is better to write them clearly separately.

The last sentence

In general, it is already a very mature approach to CSS to support setting multiple background images on one element. As long as you pay attention to the order and the writing of each attribute, there will be basically no problem.

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