# Color.fromRGBO constructor

const Color.fromRGBO(int r, int g, int b, double opacity)

Create a color from red, green, blue, and opacity, similar to `rgba()` in CSS.

- `r` is red, from 0 to 255.
- `g` is green, from 0 to 255.
- `b` is blue, from 0 to 255.
- `opacity` is alpha channel of this color as a double, with 0.0 being transparent and 1.0 being fully opaque.

Out of range values are brought into range using modulo 255.

See also fromARGB, which takes the opacity as an integer value.

## Implementation

    const Color.fromRGBO(int r, int g, int b, double opacity) :
      value = ((((opacity * 0xff ~/ 1) & 0xff) << 24) |
                ((r                    & 0xff) << 16) |
                ((g                    & 0xff) << 8)  |
                ((b                    & 0xff) << 0)) & 0xFFFFFFFF;