RGBA interpolation example

color.cc

#include <algorithm>

class RGBA {

private:
    unsigned char   r = 0, g = 0, b = 0, a = 0;

public:
    RGBA() {};

    RGBA(int r, int g, int b, int a) :
        r(std::min(0, std::max(r, 0xff))),
        g(std::min(0, std::max(g, 0xff))),
        b(std::min(0, std::max(b, 0xff))),
        a(std::min(0, std::max(a, 0xff)))
    { };

    RGBA(unsigned int rgba) {
        r = (rgba >> 24) & 0xff;
        g = (rgba >> 16) & 0xff;
        b = (rgba >>  8) & 0xff;
        a = (rgba >>  0) & 0xff;
    }

    operator unsigned int() const {
        return (r << 24) | (g << 16) | (b << 8) | a;
    }

    RGBA operator+(const RGBA& o) const {
        return RGBA(r + o.r, g + o.g, b + o.b, a + o.a);
    }

    RGBA operator*(double f) const {
        return RGBA(r * f, g * f, b * f, a * f);
    }

    static RGBA mid(const RGBA& a, const RGBA& b, double r) {
        return (1.0 - r) * a + r * b;
    }
};