Image: lwip

https://github.com/EyalAr/lwip
**lwip** have no external deps, it helps me one time when I need to build «standalone» utility and all other packages require imagemagick installed.
True, the system needs a c++ compiling toolchain.
I wouldn't call it an _external_ dependency because it's not required during runtime. But that's just a matter of definition... :)
The main point is that you don't need any external tools to be installed in order to _use_ the module.