Tips for achieving transparent background effect using CSS properties

In web design, the transparent background effect is a very common element. It can make text or pictures easier to see. However, in actual operation, we may often encounter some problems that are not ideal or cannot achieve the desired results. This article will introduce the techniques of using CSS properties to achieve transparent background effects and provide specific code examples.

First of all, we need to understand the attribute that achieves transparency in CSS, that is, opacity. This property controls the opacity of the element, ranging from 0.0 (fully transparent) to 1.0 (fully opaque). Here is a simple example:

.transparent {
  background-color: red;
  opacity: 0.5;
}

This code sets an element with a red background to 50% transparency. However, the problem is that the transparency attribute not only makes the background transparent, but also affects all content inside the element, including text and images. This is obviously not the effect we want.

So, how to achieve a transparent background without affecting the content inside the element? This requires the use of another CSS property - background-color and rgba().

The background-color property can set the background color of the element. The rgba() function can define a color value, where a represents the alpha channel, which controls the transparency. Here is an example:

.background {
  background-color: rgba(255, 255, 255, 0.5);
}

This code sets an element with a white background to 50% transparency. It should be noted that the three numbers in the rgba() function in this code represent the values ​​​​of the three colors of red, green, and blue respectively, ranging from 0-255 (can also be expressed in hexadecimal), and the last one The number represents transparency, and the value range is 0.0-1.0.

In addition to using the rgba() function, we can also use the hsla() function in CSS3 to set the transparent background color. The usage of the hsla() function is similar to the rgba() function, except that its parameters represent hue (Hue), saturation (Saturation), brightness (Lightness) and transparency (Alpha) respectively. Here is an example:

.hue {
  background-color: hsla(120, 50%, 50%, 0.5);
}

This code sets a background color with a hue of 120, a saturation of 50%, and a brightness of 50% to 50% transparency.

In addition to using the background-color attribute to set a transparent background color, we can also use CSS3's ::before and ::after pseudo-elements to achieve this effect. This method can solve the problem of some browsers not supporting alpha channel. The specific method is to add a pseudo element before and after the element and set the background color and transparency. Here's an example:

.element {
  position: relative;
  z-index: 1;
}

.element::before {
  content: "";
  background-color: rgba(255, 255, 255, 0.5);
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
}

This code sets an element to relative positioning and then sets a transparent background via the ::before pseudo-element. It should be noted that in order for the pseudo element to be below the element, its z-index attribute needs to be set to a negative value.

To sum up, transparent background is a common effect in web design. Through the above CSS properties and techniques, we can easily achieve transparent background effects, and we can deepen our understanding through specific code examples.

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