void MainWindow::on_horizontalSlider_valueChanged(int value)
{

    unsigned char *wsk;
    unsigned char *obrazek1;
    unsigned char *obrazek2;

    double wartosc = value/100.0;

    for(int i=0; i<height; i++)
    {
        wsk = img->scanLine(i);
        obrazek1 = obrazek[0].scanLine(i);
        obrazek2 = obrazek[1].scanLine(i);
        for(int j=0; j<width; j++)
        {

            wsk[4*j] = int(wartosc * obrazek2[4*j] + (1 -wartosc) * obrazek1[4*j]);
            wsk[4*j+1] =  int(wartosc * obrazek2[4*j+1] + (1 -wartosc) * obrazek1[4*j+1]);
            wsk[4*j+2] =  int(wartosc * obrazek2[4*j+2] + (1 -wartosc) * obrazek1[4*j+2]);

        }

    }
    update();
}