OpenCV 2.2 'std::ptrdiff_t' error

Go to /usr/include/opencv2/ or wherever your opencv library is installed.

cd usr/lib/include/opencv2/

Open and edit the file core/core.hpp

gedit core/core.hpp

At row 54 starts this block:

#ifndef SKIP_INCLUDES
#include <limits.h>
#include <algorithm>
#include <cmath>
#include <complex>
#include <map>
#include <new>
#include <string>
#include <vector>
#endif // SKIP_INCLUDES

Add #include <cstddef> to the list.

#ifndef SKIP_INCLUDES
#include <limits.h>
#include <algorithm>
#include <cmath>
#include <complex>
#include <map>
#include <new>
#include <string>
#include <vector>
#include <cstddef>
#endif // SKIP_INCLUDES

Done :)