void Screen::shrink(int reduc)
    { 
         if((reduc<height)&&(reduc<width))
           {  
            int newrow,newcol;
            newrow=height/reduc;
            newcol=width/reduc;
            char *newpixels=new char[newrow*newcol];
                //iterate the old block line by line            
            for ( int i = 0; i < newrow; i++)
              {
               memcpy( newpixels + (i*newcol), pixels + (i*width), newcol);  //copy only the required amount of data
              }
               //delete the old data     
            delete []pixels;      
            pixels = newpixels;
            
             } 
   }