private static int blend_add_pin(int a, int b) {
    // setup (this portion will always be the same)
    int f = (b & ALPHA_MASK) >>> 24;
    int ar = (a & RED_MASK) >> 16;
    int ag = (a & GREEN_MASK) >> 8;
    int ab = (a & BLUE_MASK);
    int br = (b & RED_MASK) >> 16;
    int bg = (b & GREEN_MASK) >> 8;
    int bb = (b & BLUE_MASK);
    // formula:
    int cr = ar + br;
    int cg = ag + bg;
    int cb = ab + bb;
    // alpha blend (this portion will always be the same)
    // (err, NOT quite the same here - this is the "correct" version using "/ 255")
    return (low(((a & ALPHA_MASK) >>> 24) + f, 0xff) << 24 |
            (peg(ar + (((cr - ar) * f) / 255)) << 16) |
            (peg(ag + (((cg - ag) * f) / 255)) << 8) |
            (peg(ab + (((cb - ab) * f) / 255)) ) );
  }