c
if (optarg && *optarg != '\0') {
    horizSubSampling = atoi(optarg);
    if (horizSubSampling == 0) {
        fprintf(stderr, "Invalid input for horizontal subsampling. It must be a non-zero integer.\n");
        exit(EXIT_FAILURE);
    }
} else {
    fprintf(stderr, "No input provided for horizontal subsampling.\n");
    exit(EXIT_FAILURE);
}
