sudo chown -R yourusename:admin /usr/local/bin
Mac-Pro:local user$ brew install imagemagick
Error: You must `brew link jpeg' before imagemagick can be installed
Mac-Pro:local user$ brew link jpeg
Linking /usr/local/Cellar/jpeg/8d...
Error: Could not symlink file: /usr/local/Cellar/jpeg/8d/bin/wrjpgcom
/usr/local/bin is not writable. You should change its permissions.