1 files changed, 111 insertions, 0 deletions
diff --git a/host/gifstream.py b/host/gifstream.py
new file mode 100755
index 0000000..a580ae1
--- /dev/null
+++ b/host/gifstream.py
@@ -0,0 +1,111 @@
+#!/usr/bin/env python3
+# This script eats CRAP and outputs a live GIF-over-HTTP stream. The required bandwidth is about 20kB/s
+
+import io
+import math
+import threading
+import struct
+import argparse
+from itertools import chain
+from contextlib import suppress
+
+from PIL import Image, ImageFile
+from flask import Flask, Response
+
+import config
+
+import crap
+
+
+frame = None
+frame_cond = threading.Condition()
+
+def framestream():
+	global frame
+	while True:
+		with frame_cond:
+			frame_cond.wait()
+			img = Image.frombuffer('RGB', (config.display_width, config.display_height), frame, 'raw', 'RGB', 0, 1)
+			yield encode_image(img)
+
+def putframe(f):
+	global frame
+	with frame_cond:
+		frame = f
+		frame_cond.notify_all()
+
+def file_headers(w, h):
+	yield (b'GIF89a'
+		+ struct.pack('<H', w) # image width
+		+ struct.pack('<H', h) # image height
+		+ b'\x70' # flags bits 2-4: color resolution = 7
+		+ b'\x00' # background color index
+		+ b'\x00' # pixel aspect ratio (1:1)
+		# Netscape headers
+		+ b'\x21' # extension block
+		+ b'\xff' # app extension
+		+ b'\x0b' # block size
+		+ b'NETSCAPE2.0' # app name
+		+ b'\x03' # sub-block size
+		+ b'\x01' # loop sub-block id
+		+ b'\x01\x00' # repeat count (0 == Infinity)
+		+ b'\x00' # block terminator
+		)
+
+def encode_image(img):
+	img = img.convert('P', palette=Image.ADAPTIVE, colors=256)
+	palbytes = img.palette.palette
+#	assert len(img.palette) in (2, 4, 8, 0x10, 0x20, 0x40, 0x80, 0x100)
+	imio = io.BytesIO()
+	ImageFile._save(img, imio, [("gif", (0, 0)+img.size, 0, 'P')])
+	return (
+		# GCE
+		  b'\x21' # extension block
+		+ b'\xf9' # graphic control extension
+		+ b'\x04' # block size
+		+ b'\x00' # flags
+		+ b'\x00\x00' # frame delay
+		+ b'\x00' # transparent color index
+		+ b'\x00' # block terminator
+		# Image headers
+		+ b'\x2c' # image block
+		+ b'\x00\x00' # image x
+		+ b'\x00\x00' # image y
+		+ struct.pack('<H', img.width) # image width
+		+ struct.pack('<H', img.height) # image height
+		+ bytes((0x80 | int(math.log(len(palbytes)//3, 2.0))-1,)) # flags (local palette and palette size)
+		# Palette
+		+ palbytes
+		# LZW code size
+		+ b'\x08'
+		# Image data. We're using pillow here because I was too lazy finding a suitable LZW encoder.
+		+ imio.getbuffer()
+		# End of image data
+		+ b'\x00'
+		)
+
+
+app = Flask(__name__)
+#app.debug = True
+
+@app.route('/')
+def hello_world():
+	return Response(chain(file_headers(config.display_width, config.display_height), framestream()), mimetype='image/gif')
+
+
+if __name__ == '__main__':
+	parser = argparse.ArgumentParser()
+	parser.add_argument('addr', default='127.0.0.1', nargs='?')
+	parser.add_argument('port', type=int, default=1337, nargs='?')
+	args = parser.parse_args()
+
+	udp_server = crap.CRAPServer(args.addr, args.port, blocking=True, log=lambda *_a: None)
+
+	def receiver():
+		for _title, frame in udp_server:
+			putframe(frame)
+	frame_runner = threading.Thread(target=receiver, daemon=True)
+	frame_runner.start()
+
+	app.run()
+	udp_server.close()