Code:
GL_ZERO source or destination (0, 0, 0, 0)
GL_ONE source or destination (1, 1, 1, 1)
GL_DST_COLOR source (Rd, Gd, Bd, Ad)
GL_SRC_COLOR destination (Rs, Gs, Bs, As)
GL_ONE_MINUS_DST_COLOR source (1, 1, 1, 1)-(Rd, Gd, Bd, Ad)
GL_ONE_MINUS_SRC_COLOR destination (1, 1, 1, 1)-(Rs, Gs, Bs, As)
GL_SRC_ALPHA source or destination (As, As, As, As)
GL_ONE_MINUS_SRC_ALPHA source or destination (1, 1, 1, 1)-(As, As, As, As)
GL_DST_ALPHA source or destination (Ad, Ad, Ad, Ad)
GL_ONE_MINUS_DST_ALPHA source or destination (1, 1, 1, 1)-(Ad, Ad, Ad, Ad)
GL_SRC_ALPHA_SATURATE source (f, f, f, 1); f=min(As, 1-Ad)