Clang/gcc use different c++ standard for header and main

I was using CImg for picture processing, which don't compile for C++11 or above:

CImg.h:48902:22: error: there are no arguments to 'pclose' that depend on a template parameter, so a declaration of 'pclose' must be available [-fpermissive]

But my program which includes CImg.h does use some C++11 feature. Can I use different C++ standard to process these two files? CImg.h itself is a header+code so I have to #include that.