if (argv[1][0]=='D'){
                demo=1;
                argv[1]++;
        }

        if (argv[1][0]=='P'){
                if (sscanf(argv[1], "P%ux%ux%ux%ux%lfx%ux%u"
                                ,&temporal_resample
                                ,&input_w, &input_h, &rate, &input_gamma
                                ,&output_w
                                ,&output_h)!=7){
                        fprintf(stderr,"%s: Invalid argument format\n", progname);
                        print_usage();
                        exit(3);
                }
                ppm=1; 
         }else{
                if (sscanf(argv[1], "%ux%ux%ux%ux%lfx%ux%u"
                                ,&temporal_resample
                                ,&input_w
                                ,&input_h
                                ,&rate
                                ,&input_gamma
                                ,&output_w
                                ,&output_h)!=7){
                        fprintf(stderr,"%s: Invalid argument format\n", progname);
                        print_usage();
                        exit(3);
                }