diff options
| -rw-r--r-- | pgm-interlace.c | 158 |
1 files changed, 144 insertions, 14 deletions
diff --git a/pgm-interlace.c b/pgm-interlace.c index 42bd44e..4e500da 100644 --- a/pgm-interlace.c +++ b/pgm-interlace.c @@ -27,13 +27,134 @@ #include <stdio.h> #include <stdlib.h> +#include <ctype.h> +#include <string.h> + +/* check header values are sane */ +int check_sanity(long width, long height, long white, unsigned int clust_total) +{ + if (width <= 0 || height <= 0) + { + fprintf(stderr, "image dimensions must be positive\n"); + return 1; + } + + /* FIXME only support single-byte pixels, PGM supports 16-bit according + * to <http://netpbm.sourceforge.net/doc/pgm.html> */ + if (white > 255) + { + fprintf(stderr, "Only a maximum gray value < 256 is supported\n"); + return 1; + } + + if (width * clust_total != height) + { + fprintf(stderr, "%d images of %ldx%ld cannot interlace to a square image %ldx%ld\n", + clust_total, width, height, height, height); + return 1; + } + return 0; +} + +void read_whitespace(FILE *fd) +{ + char c = '\0'; + do + { + c = fgetc(fd); + } while (strchr(" \t\n\r", c)); + + ungetc(c, fd); +} + +int read_token(FILE *fd, char *token, size_t token_size, char *allowable) +{ + char c = '\0'; + int t = 0; + + while (!feof(fd)) + { + /* -1 to leave room for null terminator*/ + if (t >= token_size - 1) + { + fprintf(stderr, "read_token: token too large\n"); + return 1; + } + + c = fgetc(fd); + + if (strchr(allowable, c) == NULL) + { + ungetc(c, fd); + break; + } + *(token++) = c; + } + + *token = '\0'; + + return 0; +} + +int read_number(FILE *fd, char *token, size_t token_size) +{ + return read_token(fd, token, token_size, "0123456789"); +} + +/* parse the file's header and read fields into variables */ +int parse_header(FILE *fd, char *magic, long *width, long *height, int *white) +{ + char token[32]; + int ret = 0; + read_token(fd, magic, sizeof(magic), "P5"); + + if (strcmp(magic, "P5") != 0) + { + fprintf(stderr, "magic number does not check out, stopping.\n"); + return 1; + } + + read_whitespace(fd); + + if (read_number(fd, token, sizeof(token)) != 0) + { + fprintf(stderr, "Error reading width\n"); + return 1; + } + *width = atoi(token); + read_whitespace(fd); + + if (read_number(fd, token, sizeof(token))) + { + fprintf(stderr, "Error reading height\n"); + return 1; + } + *height = atoi(token); /* size == height */ + read_whitespace(fd); + + if (read_number(fd, token, sizeof(token))) + { + fprintf(stderr, "Error reading white value\n"); + return 1; + } + *white = atoi(token); + + /* standard dictates one whitespace character */ + /* FIXME check that it's actually a whitespace char */ + fgetc(fd); + return ret; +} int main(int argc, char **argv) { - unsigned int i, x, y, size, header_size; + unsigned int i, x, y; + long width, size, new_width, new_size; + int white, new_white; unsigned int clust_total = argc-1; char buffer[4096]; FILE **f = NULL; + char magic[3]; + char new_magic[3]; if (argc == 1) { @@ -62,22 +183,31 @@ int main(int argc, char **argv) } } - /* Fetch sizes from */ - /* FIXME doesn't check magic value */ - /* FIXME extremely hackish, relies on specific whitespace format */ - fgets(buffer, sizeof(buffer), f[0]); - fgets(buffer, sizeof(buffer), f[0]); - fgets(buffer, sizeof(buffer), f[0]); - size = atoi(buffer); - fprintf(stderr, "Full image size will be %dx%d, using %d images\n", size, size, clust_total); - fgets(buffer, sizeof(buffer), f[0]); - header_size = ftell(f[0]); - for (i = 1; i < argc; i++) - fseek(f[i-1], header_size, SEEK_SET); + if (parse_header(f[0], magic, &width, &size, &white) != 0) + return 1; + + if (check_sanity(width, size, white, clust_total) != 0) + return 1; + + for (i = 1; i < clust_total; i++) + { + parse_header(f[i], new_magic, &new_width, &new_size, &new_white); + if (strcmp(magic, new_magic) != 0 + || width != new_width + || size != new_size + || white != new_white) + { + fprintf(stderr, "'%s' doesn't have identical header to '%s', stop\n", argv[i+1], argv[1]); + return 1; + } + } + + /* check that header values all agree */ + fprintf(stderr, "Full image size will be %ldx%ld, using %d images\n", size, size, clust_total); /* Output PGM Header */ - printf("P5\n%d\n%d\n255\n", size, size); + printf("P5\n%ld\n%ld\n%d\n", size, size, white); /* FIXME use a buffer * FIXME check for EOF */ |