68   int argi;  in main()  local
70   for (argi = 1; argi < argc; argi++)  in main()
72     if (argv[argi][0] == '-')  in main()
74       switch (argv[argi][1])  in main()
84           argi++;  in main()
85           if ((fp_al = fopen (argv[argi], "wb")) == NULL)  in main()
88             fprintf (stderr, "Error:  can not create alpha-channel file %s\n", argv[argi]);  in main()
99           fprintf (stderr, "Error:  unknown option %s\n", argv[argi]);  in main()
107       if ((fp_rd = fopen (argv[argi], "rb")) == NULL)  in main()
110             fprintf (stderr, "Error:  file %s does not exist\n", argv[argi]);  in main()
116       if ((fp_wr = fopen (argv[argi], "wb")) == NULL)  in main()
119         fprintf (stderr, "Error:  can not create file %s\n", argv[argi]);  in main()