Print templates for trihexaflexagons, hexahexaflexagons, etc
Your python3 needs opencv-python (which in turn uses numpy).
If everything is set up right, then examples.sh should create some useful examples, and the commands in there should give you basically an idea how to use it.
The first example you should probably start with is ex_num_tri.png or ex_col_tri.png. Make sure when printing that the aspect is not messed up -- the triangles must remain equilateral! After printing, cut out, and pre-crease every line so it can easily fold both ways.
ex_num_trif?.png (produced using trif?.cfg) are not for printing (or at least not for folding); those constitute a folding tutorial showing what ex_num_tri.png should look like after fold 1, fold 2, ... fold 5. Every fold is behind/away (origami 'mountain') not towards you (origami 'valley'). f4 is a 'flip through'. f5 should put the two blank triangles face to face, then glue-stick them together.
ex_col_tri.png is the same deal, but with colored images (generated by trainers.py) instead of numbers. The tri version uses the 3 primary colors red ylw blu. Folding according to the instructions assembles the red face. If you flex red by pinching the yellow dots and unfolding from the middle, you get to yellow. Then blue dots gets you to blue, then red dots gets you to back to red.
The hexahexaflexagons are necessarily more difficult. If you print ex_col_hex.png, after cutting out and creasing all lines, first you fold the strip in half (like trif1.cfg), then 'roll' it together by folding adjacent greens together, then adjacent purples together, etc. At that point you should have a flattened tube of paper that looks just like ex_col_f1.png, and you continue from there the same way.
When assembled, each primary (red/ylw/blu) face has two flexing possibilities, from red you can take a primary flex to get to yellow (as before), or a new secondary flex to get to orange (which is the color 'between' red and yellow). From orange you can only flex back to red. Etc.
When you're ready to create templates using your own photos/images, you can use hexacrop.py to make same-size square images (default 1000x1000) that crop your subject nicely (for instance you probably don't want triangles to chop eyesballs in half). `hexacrop.py yourimg.jpg' will raise a window with your image and a six-triangled hexagon on it. You can use wasd keys to pan the hexagon around, and ,. to shrink/expand. When you're happy with how your crop will be chopped into triangles, c will save out the crop and quit.