finished Skin UGC

nonpacks/library/zips.py

@@ -7,6 +7,7 @@ adopted file (under MEDIA_ROOT) and return plain dicts/values.
 
 import json
 import os
+import struct
 import zipfile
 
 INJECTOR_NAMES = {'V': 'Vaginal', 'M': 'Mouth', 'A': 'Anal'}
@@ -16,6 +17,48 @@ PROBLEM_TAGS = {'broken', 'bugged', 'borked'}
 MODEL_FILE_EXTENSIONS = ('.bbmodel', '.geo.json', '.jem', '.gltf', '.glb')
 
 
+def _png_size(head):
+    """(width, height) from a PNG IHDR header, or None when not a PNG."""
+    if len(head) < 24 or head[:8] != b'\x89PNG\r\n\x1a\n':
+        return None
+    return (struct.unpack('>I', head[16:20])[0], struct.unpack('>I', head[20:24])[0])
+
+
+SKIN_SIZES = {(64, 32), (64, 64), (128, 128)}
+
+
+def read_skins_manifest(path):
+    """Scan the archive for Minecraft skin PNGs (64x32, 64x64 or 128x128).
+
+    Returns None when no skins are found; otherwise {skins: [{name, member,
+    width, height}]} where ``member`` is the zip member served via pack_asset.
+    """
+    zf = _open_zip(path)
+    if zf is None:
+        return None
+    try:
+        skins = []
+        for name in sorted(n for n in set(zf.namelist()) if n.lower().endswith('.png')):
+            try:
+                with zf.open(name) as fh:
+                    head = fh.read(24)
+            except (KeyError, OSError, zipfile.BadZipFile):
+                continue
+            size = _png_size(head)
+            if size and size in SKIN_SIZES:
+                skins.append({
+                    'name': name.rsplit('/', 1)[-1],
+                    'member': name,
+                    'width': size[0],
+                    'height': size[1],
+                })
+        if not skins:
+            return None
+        return {'skins': skins}
+    finally:
+        zf.close()
+
+
 def _in_plugins_dir(name):
     """True when a member lives inside a plugins/ folder (any nesting)."""
     parts = name.split('/')