Install png package in macOsX
1- install Xcode from app store (take care, it is 4 GB !) 2- Open Xcode from application folder and install line command tools 3- Open terminal and enter: sudo xcodebuild -license 4- Go to the end and enter agree 5- Install macport https://www.macports.org (it is simpler to use the .pkg file) or/and update it using: 6- In terminal enter: sudo port upgrade outdated 7- Enter in terminal: sudo port install libpng 8- In R, enter: install.packages(pkgs=" http://www.rforge.net/src/contrib/png_0.1-8.tar.gz", repos=NULL) Done