unsigned char buff[4][4];
ifstream myfile1 ("sel.jpg", ios::binary);
ofstream myfile3  ("encrypt.jpg", ios::binary);
 
while(myfile1.read( (char *)buff, 16 ))
{	  
	  for ( j=0; j<BC; j++)
	  for ( i=0; i < 4; i++)        
	  {
		  a[i][j] = buff[j][i]; // plaintext
           }
Encrypt(a, rk);
 
if (myfile3.is_open())
	  {
		  for(j=0; j< BC; j ++)
			  for ( i=0; i<4; i++)
				  myfile3<<a[i][j];		  
	  }   
	  else        
		cout << "Unable to open file";
}	
myfile3.close();
	myfile1.close();
 
unsigned char buffer[4][4];
ifstream myfile4;
		myfile4.open( "encrypt.jpg", ios::binary);
		if( !myfile4 )
		{
      cout << "error opening file, quitting" << endl;
      return -1;
		}
	ofstream myfile5 ("test.jpg", ios::binary);
 
while(myfile4.read( (char *)buffer, 16 ))
  {
  for ( j=0; j<BC; j++)
	  for ( i=0; i < 4; i++)        
	  {		  
		  a[i][j] = buffer[j][i]; // plaintext
}
Decrypt(a, rk);
if (myfile5.is_open())
		{
		    for(j=0; j<BC; j ++)
			for ( i=0; i<4; i++)
			myfile5<<a[i][j];
		}   
		  else        
			  cout << "Unable to open file";
  }				
 
  	myfile5.close();
	myfile4.close();

long begin, end;
begin = myfile1.tellg();
myfile1.seekg(0, ios::beg);
end = myfile1.tellg();
cout<<end;
 
while(((end)%16)!==0))
{
     char pad=" ";
     myfile1<<pad;
}

myfile1.seekg(0, ios::end);

  myfile1.seekg( 0, ios::beg );

//after reading all the data in, do padding
int pad_num = 16 - (end % 16) ;  //find how many to pad
char pad = " ";
for( i = 0; i < pad_num; i++ )
{
     arr[r][c] = pad;  //assuming you're trying to fill the array out
}

// obtaining file size
#include <iostream>
#include <fstream>
using namespace std;
 
int main () {
  long begin,end;
  ifstream myfile ("example.txt");
  begin = myfile.tellg();
  myfile.seekg (0, ios::end);
  end = myfile.tellg();
  myfile.close();
  cout << "size is: " << (end-begin) << " bytes.\n";
  return 0;
}