<alpha-value>
The <alpha-value>
CSS data type represents a value that can be either a <number>
or a <percentage>
, specifying the alpha channel or transparency of a color.
Syntax
The value of an <alpha-value>
is given as either a <number>
or a <percentage>
.
If given as a number, the useful range is 0 (fully transparent) to 1.0 (fully opaque), with decimal values in between; that is, 0.5 indicates that half of the foreground color is used and half of the background color is used. Values outside the range of 0 to 1 are permitted, but are clamped to lie within the range 0 to 1.
If the alpha value is given as a percentage, 0% corresponds to fully transparent while 100% indicates fully opaque.
Formal syntax
<alpha-value> =
<number> |
<percentage>
Interpolation
When animated, values of the <alpha-value>
CSS data type are interpolated as real, floating-point numbers. The speed of the interpolation is determined by the timing function associated with the animation.
Examples
Setting text color opacity
The rgb()
function accepts a fourth optional value to specify an alpha value.
The following example shows how to apply a color with 60% opacity using the alpha value:
css
/* <rgb()> */
color: rgb(34 12 64 / 60%);
Setting shape image threshold
Here an alpha value is used to determine which parts of an image are considered part of a shape:
css
/* shape-image-threshold */
shape-image-threshold: 70%;
shape-image-threshold: 0.7;
Specifications
Specification |
---|
CSS Color Module Level 4 # type-def-alpha-value |