package math type Color struct { R, G, B, A uint8 } func (c Color) Shade(value uint8) Color { return Color{ R: c.R / value, G: c.G / value, B: c.B / value, A: c.A, } } func (c Color) Sub(value uint8) Color { return Color{ R: c.R - value, G: c.G - value, B: c.B - value, A: c.A, } }