CSS3/Color/RGBA
RGBA(Red-Green-Blue-Alpha)
The RGB color model is extended in this specification to include “alpha” to allow specification of the opacity of a color.
The format of the RGBA Value
rgba(R,G,B,A) -integer-
The format of an RGBA value in the functional notation is ‘rgba(’ followed by a comma-separated list of three numerical values (three integer values), followed by an <alphavalue>, followed by ‘)’.
rgba(R,G,B,A) -percentage-
The format of an RGBA value in the functional notation is ‘rgba(’ followed by a comma-separated list of three numerical values (three percentage values), followed by an <alphavalue>, followed by ‘)’.
Example
Alpha | hsla(H,S,L,A) | Color | |
---|---|---|---|
0.0 | rgba(255, 0, 0, 0.0) | fully transparent | |
0.2 | rgba(255, 0, 0, 0.2) | ||
0.4 | rgba(255, 0, 0, 0.4) | ||
0.6 | rgba(255, 0, 0, 0.6) | ||
0.8 | rgba(255, 0, 0, 0.8) | ||
1.0 | rgba(255, 0, 0, 1.0) | fully opaque |
Point, Note
- If RGBA values are not supported by a user agent, they should be treated like unrecognized values per the CSS forward compatibility parsing rules ([CSS21], Chapter 4). RGBA values must not be treated as simply an RGB value with the opacity ignored.
CSS Reference
The CSS Color Module Level 3 specification defines the RGBA color values in 4.2.2. RGBA color values.