th: add extractor example

bin/thumbs/README.md

@@ -46,6 +46,8 @@ copyparty performs buffered reading, so expect multiple `read()` calls, respect
 
 ## examples
 
+* [randomcolor](https://github.com/9001/copyparty/blob/hovudstraum/bin/thumbs/randomcolor.py) generates a random .gif image
+
 
 ## some other known plugins seen on the internets
 

bin/thumbs/randomcolor.py

@@ -0,0 +1,29 @@
+import io
+import os
+import struct
+from base64 import b64decode
+
+
+def create_gif() -> bytes:
+    head = r"R0lGODdhIAAgAIAB"
+    tail = r"AAD/LAAAAAAgACAAAAIehI+py+0Po5y02ouz3rz7D4biSJbmiabqyrbuC5sFADs="
+    #color = struct.pack(">L", random.randrange(0xffffff))  # wow, way too stable
+    color = b"\x00" + os.urandom(3)
+    return b64decode(head) + color + b64decode(tail)
+
+
+def main(abspath, **ka) -> Optional[tuple[str, IO[bytes], int, int, Optional[int]]]:
+    print("hello from randomcolor.py pretending to extract a thumb from " + abspath)
+
+    # need to return a file-like object
+    gif_bytes = create_gif()
+    file_obj = io.BytesIO(gif_bytes)
+
+    # where copyparty should seek to in the "file" to start reading from
+    seek_offset = 0
+    seek_whence = 0
+
+    filesize = None  # auto; read until end
+
+    # "gif" is the file-extension to decode the file as
+    return "gif", file_obj, seek_offset, seek_whence, filesize