xjpeg.c

/* Simple JPEG tag extractor and viewer. (c) Marcus Meissner 2003, LGPL */
#include <stdio.h>
#include <unistd.h>
#include <string.h>

#define APP0      0xe0
#define APP1      0xe1
#define APP2      0xe2
#define DHT 0xc4
#define SOI 0xd8
#define DQT 0xdb
#define SOF0      0xc0
#define SOS 0xda
#define COM 0xfe

static int
rb(int suppress) {
      unsigned char c;

      if (1!=read(fileno(stdin),&c,1))
            return -1;
      if (!suppress)
            fprintf(stderr,"%02x",c);
      return c;
}

static int
rd(int len, char *data) {
      unsigned int c,i;

      for (i=0;i<len;i++) {
            c = rb(1);
            if (c == -1) return -1;
            if (c == 0xff) c = rb(1);
            if (c == -1) return -1;
            data[i] = c;
      }
      return len;
}

static int
getmarker(void) {
      int c;
      
      c = rb(0);
      if (c == -1) return -1;
      if (c!=0xff) return -1;
      c = rb(0);
      return c;
}

static int
getlength(void) {
      int x1,x2;
      
      x1 = rb(1);
      if (x1 == -1) return -1;
      x2 = rb(1);
      if (x2 == -1) return -1;
      x1 =  (x1 << 8) | x2;
      fprintf(stderr,"(%d)",x1);
      return x1;
}

static int
skipdata(int len, int suppress) {
      int x,i;

      for (i=0;i<len;i++) {
            x = rb(suppress);
            if (x == -1)
                  return x;
            if (x == 0xff) {
                  x = rb(suppress);
                  if (x == -1)
                        return x;
            }
      }
      return 1;
}

static int
haslength(int marker) {
      switch (marker) {
      case SOI:   return 0;
      case APP0:  return 1;
      case APP1:  return 1;
      case APP2:  return 1;
      case DHT:   return 1;
      case SOS:   return 1;
      case DQT:   return 1;
      case COM:   return 1;
      default:    return 1;
      }
}

static int
print_jfif() {
      int major, minor, density, x, y, r, tx, ty ;
      r = rb(1); if (r == -1) return -1;

      major = rb(1);
      if (major == -1) return -1;
      minor = rb(1);
      if (minor == -1) return -1;
      density = rb(1);
      if (density == -1) return -1;

      x = rb(1); if (x == -1) return -1;
      r = rb(1); if (r == -1) return -1;
      x = (x << 8) | r;

      y = rb(1); if (y == -1) return -1;
      r = rb(1); if (r == -1) return -1;
      y = (y << 8) | r;
      tx = rb(1); if (tx == -1) return -1;
      ty = rb(1); if (ty == -1) return -1;
      fprintf(stderr,"JFIF v%d.%d, dens %d, %dx%d, tn %dx%d\n", major, minor, density, x, y, tx, ty);
      return skipdata(tx * ty * 3,1);
}

int
main(int argc, char **argv) {
      int m, len;

      m = getmarker();
      if (m != SOI) {
            fprintf(stderr,":unknown, aborting.\n"); 
            return 1;
      }
      fprintf(stderr,":SOI\n");
      while (1) {
            m = getmarker();
            if (m == -1) {
                  fprintf(stderr,":Error, end of file, aborting.\n");
                  break;
            }
            if (haslength(m))
                  len = getlength();
            else
                  len = 0;
            switch (m) {
            case COM: {
                  char *comment;
                  
                  comment = malloc(len - 2 + 1);
                  comment[len-2]='\0';
                  if (-1 == rd(len - 2, comment))
                        break;
                  fprintf(stderr,":COM(%s)\n",comment);
                  break;
            }
            case SOS: {
                  int i,ns,ss,se,ahl,cs,td;

                  ns = rb(1);if (ns == -1) break;
                  fprintf(stderr,":SOS ");
                  for (i=0;i<ns;i++) {
                        cs = rb(1);if (cs == -1) break;
                        td = rb(1);if (td == -1) break;
                        fprintf(stderr,"[%d,%d:%d]",cs,(td>>4),td&0xf);
                  }
                  ss = rb(1); if (ss == -1) break;
                  se = rb(1); if (se == -1) break;
                  ahl = rb(1); if (ahl == -1) break;
                  fprintf(stderr,"ss=%d, se=%d, h=%d,l=%d\n",ss,se,(ahl>>4),ahl&0xf);
                  break;
            }
            case SOF0: {
                  int bitcnt,x,y,nf,i,c,hv,tq;
                  m = rb(1); if (m == -1) break;
                  bitcnt = m;
                  y = rb(1); if (y == -1) break;
                  m = rb(1); if (m == -1) break;
                  y = (y<<8) | m;
                  x = rb(1); if (x == -1) break;
                  m = rb(1); if (m == -1) break;
                  x = (x<<8) | m;
                  nf = rb(1); if (nf == -1) break;

                  fprintf(stderr,":SOF0,bitcnt=%d,x=%d,y=%d:\n",bitcnt,x,y);
                  for (i=0;i<nf;i++) {
                        c = rb(1); if (c == -1) break;
                        hv = rb(1); if (hv == -1) break;
                        tq = rb(1); if (tq == -1) break;
                        fprintf(stderr,"\t %02x = %d:%d, tq=%d\n",c,(hv>>4),hv&0xf,tq);
                  }
                  break;
            }
            case DHT: {
                  m = rb(1);
                  if (m == -1) break;
                  fprintf(stderr,":DHT(0x%02x)\n",m);
                  skipdata(len - 2 - 1,1);
                  break;
            }
            case DQT: {
                  fprintf(stderr,":DQT\n");
                  skipdata(len-2,1);
                  break;
            }
            case APP1: case APP2:
            case APP0: {
                  char name[5];
                  fprintf(stderr,":APP0(");
                  if (-1==rd(4,name))
                        break;
                  name[4] = '\0';
                  fprintf(stderr,"%s):", name);
                  if (!strcmp(name,"JFIF")) {
                        print_jfif();
                  } else {
                        if (-1==skipdata(len - 2 - 4,0)) {
                              break;
                        }
                        fprintf(stderr,"\n");
                  }
                  break;
            }
            default:
                  fprintf(stderr,":Unknown marker\n");
                  if (len) {
                        if (-1==skipdata(len - 2,0)) {
                              break;
                        }
                        fprintf(stderr,"\n");
                  }
                  break;
            }
      }
      return 0;
}