int pow4(int in, int curve) __attribute__((noinline)) {
  float x = int2f(in);

  // Transform curve param to float in 0 - 1 range
  float a = int2f(curve << 21);
  // Reverse curve param
  a = 1 - a;

  // Interpolate between exp-like and log-like curves (without using pow())
  // With thanks to Johannes for code
  float outf = a * (x * x * x * x) +
               (1 - a) * (1 - (1 - x) * (1 - x) * (1 - x) * (1 - x));
  return f2int(outf);
}

float int2f(int32_t val) __attribute__((noinline)) {
  return val * (float)(1.0f / (1 << 27));
}

int32_t f2int(float val) __attribute__((noinline)) {
  return (int)(val * (float)(1 << 27));
}

int scale(int in, int hi, int lo) __attribute__((noinline)) {
  return (___SMMUL((((hi << 21) - (lo << 21)) >> 1), in) << 6) + (lo << 21);
}