G ++与libpng链接

Question

I'm trying to do some image processing using C++. I'm currently using OS X 10.7 and writing my code simply using a makefile and the terminal. I've used macports to install libpng but I still can't link with it.

g++ main.cpp -llibpng -O2 -o ImageManipulator

g++ main.cpp -lpng -O2 -o ImageManipulator

both fail with:

ld: library not found for -lpng

and

ld: library not found for -llibpng

does anyone know how to call g++ for this on OS X?

Answer 1

I dont think macports does add its lib directory to the default path searched by gcc. Try

g++ main.cpp -L/opt/local/lib -lpng -O2 -o ImageManipulator

Answer 2

使用-L / path / to / library_directory让g ++知道在哪里找到libpng（我已经忘记了mac ports安装库的地方）。

Answer 3

Got this error trying to install a gem (Mac OSX / Homebrew). Fixed by running brew update && brew install libpng && brew link libpng --force