Minecraft Skin PNG Toolkit

A local Python PNG structure inspector, editing checklist, source-linked troubleshooting CSV and unit tests. Requires Python 3.9 or newer; no packages or network access required. Checks PNG signature, IHDR, chunk boundaries and CRCs, plus IDAT/IEND presence; reports dimensions, color type and alpha-channel metadata as JSON. Extract the source ZIP and run python skin_png_check.py my-skin.png; run tests with python -m unittest -v. Does not decode pixels, fully validate PNG semantics, detect skin models, validate UV layouts or guarantee Minecraft edition compatibility. An alpha channel does not prove transparent pixels exist. MIT licensed. Code and text authored with generative AI assistance. The companion browser editor is Block Skin Maker: https://blockskinmaker.com/ . Not affiliated with Mojang or Microsoft.