I’m trying to enable the jpeg image writing command as described at
in section 3.5.4.
What I can’t figure out is where to insert those additional Make lines.
The Makefile in Obj_serial (I’m using “make serial”) is created by the make process somewhere so modifying it to match the instructions doesn’t work because it just gets rewritten.
Adding the lines to the main Makefile also doesn’t work.
The information you are looking for is presented earlier in the documentation: 3.2. Build LAMMPS with make — LAMMPS documentation
src/MAKE/MINE/Makefile.serial to your liking. Use the embedded comments as guide.
Or use the CMake build procedure where support for image file formats and multiple other things is auto-detected and thus setting explicit flags rarely required.