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	treciprocity.c - filmtools - various tools for photographic film development an…
	git clone git://src.adamsgaard.dk/filmtools
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	treciprocity.c (2131B)
	---
	1 #include <stdio.h>
	2 #include <unistd.h>
	3 #include <err.h>
	4 #include <math.h>
	5 #include <string.h>
	6
	7 #define LENGTH(X) (sizeof X / sizeof X[0])
	8
	9 typedef struct {
	10 const char *manufacturer;
	11 const char *name;
	12 double factor;
	13 double exponent;
	14 } Film;
	15
	16 static const Film films[] = {
	17 { "ilford", "panf", 1.00, 1.33 },
	18 { "ilford", "fp4", 1.00, 1.26 },
	19 { "ilford", "hp5", 1.00, 1.31 },
	20 { "ilford", "delta100", 1.00, 1.26 },
	21 { "ilford", "delta400", 1.00, 1.41 },
	22 { "ilford", "delta3200", 1.00, 1.33 },
	23 { "ilford", "sfx", 1.00, 1.43 },
	24 { "ilford", "xp2", 1.00, 1.31 },
	25 { "fujifilm", "acros", 0.96, 1.02 },
	26 { "kodak", "tmx", 1.18, 1.13 },
	27 { "kodak", "tmy", 1.05, 1.22 },
	28 { "kodak", "tmz", 1.34, 1.20 },
	29 { "kodak", "trix", 2.41, 1.29 },
	30 };
	31
	32 char *argv0;
	33
	34 static void
	35 usage()
	36 {
	37 int i;
	38
	39 printf("usage: %s film time\n", argv0);
	40 puts("where time is metered exposure time in seconds or format M…
	41 puts("and film is one of the following:");
	42 for (i = 0; i < LENGTH(films); i++)
	43 printf(" %-12s (%s)\n", films[i].name, films[i].manuf…
	44 }
	45
	46 int
	47 main(int argc, char **argv)
	48 {
	49 double factor, exponent, sec_equiv;
	50 int i, hour, min, sec;
	51
	52 argv0 = *argv;
	53
	54 #ifdef __OpenBSD__
	55 if (pledge("stdio", NULL) == -1)
	56 errx(1, "pledge");
	57 #endif
	58
	59 if (argc != 3) {
	60 usage();
	61 errx(1, "incorrect arguments");
	62 }
	63
	64 for (i = 0;; i++) {
	65 if (i == LENGTH(films))
	66 errx(3, "unknown film type");
	67 if (strncasecmp(argv[1], films[i].name, 10) == 0) {
	68 factor = films[i].factor;
	69 exponent = films[i].exponent;
	70 break;
	71 }
	72 }
	73
	74 if (sscanf(argv[2], "%d:%d", &min, &sec) != 2) {
	75 if (sscanf(argv[2], "%d", &sec) == 1) {
	76 min = 0;
	77 } else {
	78 errx(2, "could not parse time in seconds or MM:S…
	79 }
	80 }
	81
	82 sec_equiv = factor * pow(min * 60 + sec, exponent);
	83 sec = (int)(sec_equiv) % 60;
	84 if ((min = (int)(sec_equiv / 60.0)) >= 60) {
	85 hour = (int)(min/60.0);
	86 min -= (int)(hour*60.0);
	87 printf("%d:%02d:%02d\n", hour, min, sec);
	88 } else {
	89 printf("%d:%02d\n", min, sec);
	90 }
	91
	92 return 0;
	93 }