LAB 5 COMPRESIA

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cstring>
using namespace std;

int main()
{
    int i;
    int R0;
    int  G0;
    int B0;
    int R;
    int   G;
    int B;
    FILE *fin;
    FILE *fout;

    fin = fopen("i23.bmp", "rb");
    fout = fopen("i23_enc.bmp", "wb");
    if (fin == NULL)
    {
        printf("Open file error.\n");
        exit(1);
    }
    int sth;
    for(int j=0; j<=54; j++)
    {
        fseek(fin, j, SEEK_SET); //seek set come back to begging of file
        sth = fgetc(fin);
        fputc(sth, fout);
    }
    fseek(fin, 1, SEEK_END);
    long int size = ftell(fin);
    fseek(fin, 55, SEEK_SET);
    R0 = fgetc(fin);
    fputc(R0, fout);
    fseek(fin, 56, SEEK_SET);
    G0 = fgetc(fin);
    fputc(G0, fout);
    fseek(fin, 57, SEEK_SET);
    B0 = fgetc(fin);
    fputc(R0, fout);
    cout<<"RGB enc: "<<R0<<" "<<G0<<" "<<B0;
    int r, g, b;
    i = 58;
    while(1)
    {
        if (i > size) break;
        fseek(fin, i, SEEK_SET);
        if(i%3==1)
        {
            r = fgetc(fin);
            R = R0 - r;
            R0 = r;
            fputc(R, fout);
        }
        if(i%3==2)
        {
            g = fgetc(fin);
            G = G0 - g;
            G0 = g;
            fputc(G, fout);
        }
        if(i%3==0)
        {
            b = fgetc(fin);
            B = B0 - b;
            B0 = b;
            fputc(B, fout);
        }
        i++;

    }
    fclose(fin);
    fclose(fout);

    fin = fopen("i23_enc.bmp", "rb");
    fout = fopen("i23_dec.bmp", "wb");
    if (fin == NULL) {
        printf("Cannot open file.\n");
        exit(1);
    }
    for(int j=0; j<=54; j++)
    {
        fseek(fin, j, SEEK_SET);
        sth = fgetc(fin);
        fputc(sth, fout);
    }
    fseek(fin, 1, SEEK_END);
    size = ftell(fin);
    fseek(fin, 55, SEEK_SET);
    R0 = fgetc(fin);
    fputc(R0, fout);
    fseek(fin, 56, SEEK_SET);
    G0 = fgetc(fin);
    fputc(G0, fout);
    fseek(fin, 57, SEEK_SET);
    B0 = fgetc(fin);
    fputc(R0, fout);
    cout<<endl<<"RGB dec: "<<R0<<" "<<G0<<" "<<B0;
    i = 58;
    while(1)
    {
        if (i > size) break;
        fseek(fin, i, SEEK_SET);
        if(i%3==1)
        {
            r = fgetc(fin);
            R = R0 - r;

            R0 = R;
            fputc(R, fout);
        }
        if(i%3==2)
        {
            g = fgetc(fin);
            G = G0 - g;

            G0 = G;
            fputc(G, fout);
        }
        if(i%3==0)
        {
            b = fgetc(fin);
            B = B0 - b;

            B0 = B;
            fputc(B, fout);
        }
        i++;

    }

    return 0;
}