EXIF Tag Viewer

//Kevin Brough
//kmb180
#include <stdio.h>
#include <string.h>
struct header{
    char start[2];
    char app1[2];
    char len_app_1[2];
    char exif_data_string[4];
    char NULL_zero[2];
    char endian[2];
    char v_num[2];
    int offset;
};
struct tiff_header{
    short tag_identifier;
    char data_type[2];
    int num_bytes;
    int data_offset;
};
int main(int argc, char *argv[]){
    FILE *f;
    struct tiff_header tiff_hdr;
    struct header hdr;
    unsigned short count = 0;
    int index = 0;
    int E0 = 224;
    int file_tracker = 12;//to keep track of where we last had the file pointer; begins at 12 because that's where the tags start
    char data_string[256];
    unsigned int u_int1; // for displaying ratios for type 5 data
    unsigned int u_int2;
    f = fopen(argv[1], "rb");
    fread(&hdr, sizeof(hdr), 1, f);
    if(hdr.app1[1] == E0){
        printf("Error: Expected APP1");
        return 1;
    }
    if(strcmp(hdr.endian, "MM") == 0){ // If what we got was MM is indeed MM then end program with error
        printf("Error: Endianess not supported");
        return 1;
    }
    fread(&count, sizeof(unsigned short), 1, f);
    for(index; index<count; index++){
        fread(&tiff_hdr, sizeof(tiff_hdr), 1, f);
        if(tiff_hdr.tag_identifier == 0x010F){
            file_tracker = ftell(f);
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);
            fread(data_string, tiff_hdr.num_bytes, 1, f);
            printf("Manufacturer:\t%s\n", data_string);
            fseek(f, file_tracker, SEEK_SET);
        }
        if(tiff_hdr.tag_identifier == 0x0110){
            file_tracker = ftell(f);
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);
            fread(data_string, tiff_hdr.num_bytes, 1, f);
            printf("Model:\t\t%s\n", data_string);
            fseek(f, file_tracker, SEEK_SET);
        }
        if(tiff_hdr.tag_identifier == 0xffff8769){
            index = 0;//restarting the loop
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);//getting to the new tags
            fread(&count, sizeof(unsigned short), 1, f); //and reading in that new count right after
        }
        if(tiff_hdr.tag_identifier == 0xffffA002){//type 4
            file_tracker = ftell(f);
            printf("Width:\t\t%u pixels\n", tiff_hdr.data_offset);
        }
        if(tiff_hdr.tag_identifier == 0xffffA003){//type 4
            file_tracker = ftell(f);
            printf("Height:\t\t%u pixels\n", tiff_hdr.data_offset);
        }
        if(tiff_hdr.tag_identifier == 0xffff8827){ //type 4
            file_tracker = ftell(f);
            printf("ISO:\t\tISO %u\n", tiff_hdr.data_offset);
        }
        if(tiff_hdr.tag_identifier == 0xffff829a){//type 5
            file_tracker = ftell(f);
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);
            fread(&u_int1, sizeof(unsigned int), 1, f);//like with the rest of these type 5's we're reading in to unsigned ints
            fread(&u_int2, sizeof(unsigned int), 1, f);
            printf("Exposure Time:\t%u/%u second\n", u_int1, u_int2);
            fseek(f, file_tracker, SEEK_SET);
        }
        if(tiff_hdr.tag_identifier == 0xffff829d){//type 5
            file_tracker = ftell(f);
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);
            fread(&u_int1, sizeof(unsigned int), 1, f);
            fread(&u_int2, sizeof(unsigned int), 1, f);
            printf("F-stop:\t\tf/%.1f\n", (double)u_int1/u_int2);
            fseek(f, file_tracker, SEEK_SET);
        }
        if(tiff_hdr.tag_identifier == 0xffff920A){//type 5
            file_tracker = ftell(f);
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);
            fread(&u_int1, sizeof(unsigned int), 1, f);
            fread(&u_int2, sizeof(unsigned int), 1, f);
            printf("Focal Length:\t%u mm\n", u_int1/u_int2);
            fseek(f, file_tracker, SEEK_SET);
        }
        if(tiff_hdr.tag_identifier == 0xffff9003){
            file_tracker = ftell(f);
            fseek(f, tiff_hdr.data_offset+12, SEEK_SET);
            fread(data_string, tiff_hdr.num_bytes, 1, f);
            printf("Date Taken:\t%s\n", data_string);
            fseek(f, file_tracker, SEEK_SET);
        }
        file_tracker += 12;
    }
    fclose(f);
    return 0;
}