Multithreaded image processing in C++

#pragma omp parallel for
for (i=0; i < numPixels; i++)
{
   pGrayScaleBitmap[i] = (unsigned BYTE)
       (pRGBBitmap[i].red * 0.299 +
        pRGBBitmap[i].green * 0.587 +
        pRGBBitmap[i].blue * 0.114);
}

* pthread_create, pthread_detach.
* pthread_mutexattr_init, pthread_mutexattr_settype, pthread_mutex_init,
* pthread_mutexattr_destroy, pthread_mutex_destroy, pthread_mutex_lock,
* pthread_mutex_trylock, pthread_mutex_unlock, pthread_mutex_timedlock.
* sem_init, sem_destroy, sem_post, sem_wait, sem_trywait, sem_timedwait.

/*ThreadA:*/ while(1){  mutex.lock();  printf("an");  usleep(100000); mutex.unlock(); }
/*ThreadB:*/ while(1){  mutex.lock();  printf("bn");  usleep(100000); mutex.unlock(); }

#pragma omp parallel for
for (i=0; i < numPixels; i++)
{ ...}

parallel_for(0,numPixels,1,ToGrayScale());

parallel_for(0,numPixels,1,[&](int i)
{
   pGrayScaleBitmap[i] = (unsigned BYTE)
       (pRGBBitmap[i].red * 0.299 +
        pRGBBitmap[i].green * 0.587 +
        pRGBBitmap[i].blue * 0.114);
});