Try stitching 2x2, cleanup
Add terrain matrix

https://minecraftwiki.net/File:TerrainGuide.png
Working terrain stitching
Add items stitching
Move stitch coordinates to stitchpack_data.js
Add JSON data file for stitched locations
Write stitchpack.json
Include tile h/w in stitchpack.json
Call stitcher from generate.js
Attempt at writing stitchpack zip. Ref GH-3