I am on Apple M1 Big Sur. I installed R and libpng using homebrew.
When I try to install the png package, the error is:
/opt/homebrew/opt/llvm/bin/clang -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/opt/homebrew/Cellar/r/4.1.1/lib/R/lib -L/opt/homebrew/opt/llvm/lib -L/opt/homebrew/Cellar/gettext/0.21/lib -L/opt/homebrew/Cellar/libpng/1.6.37/lib -o png.so read.o write.o -L/opt/homebrew/Cellar/r/4.1.1/lib/R/lib -lR -lintl -Wl,-framework -Wl,CoreFoundation
/bin/sh: libpng-config: command not found
Error: package or namespace load failed for ‘png’ in dyn.load(file, DLLpath = DLLpath, ...):
unable to load shared object '/opt/homebrew/lib/R/4.1/site-library/00LOCK-png/00new/png/libs/png.so':
dlopen(/opt/homebrew/lib/R/4.1/site-library/00LOCK-png/00new/png/libs/png.so, 6): Symbol not found: _png_create_info_struct
Referenced from: /opt/homebrew/lib/R/4.1/site-library/00LOCK-png/00new/png/libs/png.so
Expected in: flat namespace
in /opt/homebrew/lib/R/4.1/site-library/00LOCK-png/00new/png/libs/png.so
Error: loading failed
Execution halted
Please help, thanks!