ppm.c

   1 #include <ctype.h>
   2 #include <fcntl.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9
  10 static int nextchar(int fd)
  11 {
  12         unsigned char b[4] = {0};
  13         read(fd, b, 1);
  14         return b[0];
  15 }
  16
  17 static int cutint(int fd)
  18 {
  19         int c;
  20         int n = 0;
  21         do {
  22                 c = nextchar(fd);
  23         } while (isspace(c));
  24         while (isdigit(c)) {
  25                 n = n * 10 + c - '0';
  26                 c = nextchar(fd);
  27         }
  28         return n;
  29 }
  30
  31 char *ppm_load(char *path, int *h, int *w)
  32 {
  33         char *d;
  34         int fd = open(path, O_RDONLY);
  35         if (fd < 0 || nextchar(fd) != 'P' || nextchar(fd) != '6')
  36                 return NULL;
  37         *w = cutint(fd);        /* image width */
  38         *h = cutint(fd);        /* image height */
  39         cutint(fd);             /* max color val */
  40
  41         d = malloc(*h * *w * 3);
  42         read(fd, d, *h * *w * 3);
  43         close(fd);
  44         return d;
  45 }
  46
  47 void ppm_save(char *path, char *s, int h, int w)
  48 {
  49         char sig[128];
  50         int fd;
  51         sprintf(sig, "P6\n%d %d\n255\n", w, h);
  52         fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0600);
  53         write(fd, sig, strlen(sig));
  54         write(fd, s, h * w * 3);
  55         close(fd);
  56 }