installation error

[subinoy]

install_github("dahtah/imager")
Downloading github repo dahtah/imager@master
Installing imager
'/Library/Frameworks/R.framework/Resources/bin/R' --no-site-file --no-environ --no-save --no-restore CMD INSTALL
'/private/var/folders/c1/1c9zflnx7937x6nrh4tst_dm0000gn/T/RtmpJacwHO/devtools5eb22d9f388b/dahtah-imager-345279d'
--library='/Users/subinoybiswas/R_package' --install-tests

• installing source package ‘imager’ ...
  Warning in .write_description(db, file.path(outDir, "DESCRIPTION")) :
  Unknown encoding with non-ASCII data: converting to ASCII
  ** libs
  llvm-g++-4.2 -arch x86_64 -I/Library/Frameworks/R.framework/Resources/include -DNDEBUG -I/opt/X11/lib -I/usr/X11R6/include -I/usr/local/include -I"/Users/subinoybiswas/R_package/Rcpp/include" -fPIC -mtune=core2 -g -O2 -c RcppExports.cpp -o RcppExports.o
  llvm-g++-4.2 -arch x86_64 -I/Library/Frameworks/R.framework/Resources/include -DNDEBUG -I/opt/X11/lib -I/usr/X11R6/include -I/usr/local/include -I"/Users/subinoybiswas/R_package/Rcpp/include" -fPIC -mtune=core2 -g -O2 -c colourspace.cpp -o colourspace.o
  CImg.h: In member function ‘cimg_library::CImg& cimg_library::CImg::RGBtosRGB() [with T = double]’:
  colourspace.cpp:63: instantiated from here
  CImg.h:19851: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
  /usr/include/architecture/i386/math.h:343: note: candidate 1: double pow(double, double)
  /usr/include/c++/4.2.1/cmath:357: note: candidate 2: float std::pow(float, float)
  CImg.h: In member function ‘cimg_library::CImg& cimg_library::CImg::sRGBtoRGB() [with T = double]’:
  colourspace.cpp:71: instantiated from here
  CImg.h:19834: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
  /usr/include/architecture/i386/math.h:343: note: candidate 1: double pow(double, double)
  /usr/include/c++/4.2.1/cmath:357: note: candidate 2: float std::pow(float, float)
  make: *** [colourspace.o] Error 1
  ERROR: compilation failed for package ‘imager’
• removing ‘/Users/subinoybiswas/R_package/imager’
  Error: Command failed (1)