DCGs and helper predicates for parsing and coverting colours.

author

- James Cash

 colour(-Colour)// is det

DCG for parsing a colour in one of the many formats supported by Tailwind/Girouette -- a preset list of colours, rgb, rgba, hsl, hsla.

 has_alpha(+Colour) is semidet

Predicate that succeeds when Colour has an alpha component.

 colour_with_alpha(+Colour0, +Alpha, -Colour1) is semidet

When Colour0 is a colour without an alpha channel, unifies Color1 with Colour0 but having the alpha value Alpha.

 as_transparent(+Colour0, -Colour1) is det

True when Colour1 is Colour0 but with an alpha channel specified.

 colour_css(+Colour, -CssStr) is det

Unifies CssStr with the CSS string representation of Colour.