Detailed explanation of CSS transparent image properties: opacity and background-image

Detailed explanation of CSS transparent image properties: opacity and background-image

In web design and development, we often need to perform some special processing on images, including using The picture is transparent. In CSS, there are two commonly used properties to achieve image transparency, namely the opacity property and the background-image property. These two properties are described in detail below, with specific code examples.

1. Opacity attribute

The opacity attribute is used to set the transparency of an element. It accepts a value between 0 and 1, where 0 means completely transparent and 1 means completely opaque.

For example, we can create a div element, set its background to an image, and then adjust the opacity attribute to achieve the image transparency effect.

HTML code:

<div class="transparent-image"></div>

CSS code:

.transparent-image {
  background-image: url("image.jpg");
  opacity: 0.5;
}

In this example, the background image of the div element is image.jpg, and the opacity attribute is set to 0.5, which means The image transparency is 50%. You can adjust the opacity value to control the transparency of the image as needed.

It should be noted that using the opacity attribute will make the element and its content transparent. If you just want to make the image transparent without affecting other content, consider using the background-image attribute.

2. Background-image attribute

The background-image attribute is used to set the background image of the element. By setting a background image, we can use its transparent part to achieve the image transparency effect.

HTML code:

<div class="transparent-image"></div>

CSS code:

.transparent-image {
  background-image: url("image.png");
}

In this example, the background image of the div element is image.png. If the image has transparent parts, the background of the div element will also appear transparent.

It should be noted that in order to ensure that the background image can display the transparency effect correctly, we need to set the size of the div element to be consistent with the size of the background image. You can use the CSS background-size property to control the size of the background image.

CSS code:

.transparent-image {
  background-image: url("image.png");
  background-size: cover;
  width: 300px;
  height: 200px;
}

In this example, the width and height of the div element are set to 300px and 200px respectively, and the background-size attribute is set to cover, indicating that the background image will be proportional Scales to fit the width and height of the element.

Through the above method, you can choose to use the opacity attribute or the background-image attribute to achieve image transparency according to actual needs. If you need to make both the element and its content transparent, you can use the opacity attribute; if you only need to make the image transparent, you can use the background-image attribute.

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