CSS Data Type - <alpha-value>

CSS <alpha-value> data type determines the transparency or alpha channel of a color. It can be a <number> (between 0 and 1) or a <percentage> (between 0% and 100%).

Possible Values

  • <number> − It represents a decimal number between 0 (fully transparent) to 1. 0 (fully opaque).

  • <percentage> − It represents a percentage between 0% (fully transparent) and 100% (fully opaque).

Syntax

<alpha-value> = number | percentage;

CSS <alpha-value> - Text Color Opacity

The following example demonstrates different heading elements using the rgba() function with both number and percentage values, in order to check the opacity of the text color. In the following example −

  • rgba(255, 0, 0, 0.6) represents the color with RGB components (255, 0, 0) and the fourth value (0.6) represents the alpha channel or opacity.
  • rgba(109, 101, 233, 70%) represents the color with RGB components (109, 101, 233) and an alpha channel of 70%, indicating the opacity.
<html>
<head>
<style>
   h3 {
      color: rgba(255, 0, 0, 0.6);
   }
   h4 {
      color: rgba(109 101 233 / 70%);
   }
</style>
</head>
<body>
   <h3>Text color opacity with number value.</h3>
   <h4>Text color opacity with percentage value.</h4>
</body>
</html>

CSS <alpha-value> - shape-image-threshold Property

The following example demonstrates the use of shape-image-threshold property, that sets the alpha channel threshold to determine a shape of an image −

<html>
<head>
<style>
   .img-container {
      width: 400px;
      height: 200px;
      background-image: url("images/pink-flower.jpg");    
      color: yellow;
      shape-image-threshold: 0.8; 
   }
</style>
</head>
<body>
   <div class="img-container">
      <h1>This text will wrap around the shape of the image.</h1>
   </div>
</body>
</html>
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