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What does a in rgba mean? How to use rgba

云罗郡主

Nov 21, 2018 pm 05:29 PM

The content of this article is about what does a in rgba mean? How to use rgba. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

RGBA color

RGB is a color standard, which is a variety of colors obtained by the changes and superposition of red (R), green (G), and blue (B). . To put it bluntly, RGBA adds a transparency channel Alpha to RGB.

Syntax:

rgba (R, G, B, A)

Description:

R: Red value (Red);

G: Green value (Green);

B: Blue value (Blue);

A: Transparency (Alpha);

R, G, B three Each parameter can be a positive integer or a percentage. The positive integer value ranges from 0 to 255, and the percentage value ranges from 0.0% to 100.0%. Values outside the range are rounded to the nearest value limit. Not all browsers support using percentage values.

Parameter A is transparency, similar to the opacity attribute. The value range is between 0.0~1.0 and cannot be negative. The following is the correct usage of RGBA colors:

rgba(255,255,0,0.5)
rgba(50%,80%,50%,0.5)

Example:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head> 
    <title>CSS3 RGBA颜色</title>
    <style type="text/css">
        *{padding:0;margin:0;}
        ul
        {
            display:inline-block;
            list-style-type:none;
            width:200px;
        }
        li
        {
            height:30px;
            line-height:30px;
            font-size:20px;
            font-weight:bold;
            text-align:center;
        }
        /*第1个li*/
        li:first-child
        {
            background-color:#FF00FF;
        }
        /*第2个li*/
        li:nth-child(2)
        {
            background-color:rgba(255,0,255,0.5);
        }
        /*第3个li*/
        li:last-child
        {
            background-color:#FF00FF;
            opacity:0.5;
        } 
    </style>
</head>
<body>
    <ul>
        <li>php中文网</li>
        <li>php中文网</li>
        <li>php中文网</li>
    </ul>
</body>
</html>

The effect is as follows:

What does a in rgba mean? How to use rgba

## Analysis:

The hexadecimal color value #FF00FF is equivalent to rgb(255,0,255). The first li element does not use RGBA color values, nor does it use the transparency opacity attribute; the second li element uses RGBA color values; the third li element uses the transparency opacity attribute.

You can clearly see that if we use the transparency opacity attribute on an element, the content of the element and its sub-elements will be affected.

We know from the above example that RGBA is better than the transparency opacity attribute for setting the transparency of an element, because RGBA will not affect the content in the element and the opacity of sub-elements.

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