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steg-decode.c
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steg-decode.c
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/*
* steg-decode.c
* IJC-DU1
* Author : Pomsar Jakub
* Organization : VUT FIT
* Date : March 15, 2022
* Compiled : gcc version 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04)
*/
#include <stdio.h>
#include <stdlib.h>
#include "bitset.h"
#include "ppm.h"
#include "error.h"
#include "eratosthenes.h"
int main(int argc, char *argv[])
{
if(argc == 2)
{
struct ppm *image = ppm_read(argv[1]);
if(image == NULL)
{
error_exit("steg-decode: Chyba\n");
}
int size_of_image = (image->xsize * image->ysize * RGB);
bitset_alloc(arr_eras,size_of_image);
Eratosthenes(arr_eras);
char buffer = 0,offset = 0;
int null_char_found = 0;
for(int i = 29; i < size_of_image; i++)
{
if(!bitset_getbit(arr_eras,i))
{
if((image->data[i+1] & 1)) buffer |= (1 << offset);
offset++;
if(offset == CHAR_BIT)
{
if(buffer == 0)
{
null_char_found = 1;
break;
}
else
{
offset = 0;
printf("%c",buffer);
buffer = 0;
}
}
}
}
printf("\n");
if(!null_char_found) error_exit("Nenalezen koncici znak\n");
bitset_free(arr_eras);
ppm_free(image);
}
else error_exit("steg-decode:Spatny pocet zadanych argumentu!\n");
return 0;
}