bus analyser: add a frame extraction cli command

bus_analyzer/bus_analyzer/extract.py

@@ -5,6 +5,7 @@ from io import BytesIO
 import argh
 from PIL import Image, ImageStat
 
+import common
 from common.segments import extract_frame, parse_segment_path
 
 
@@ -186,6 +187,17 @@ def create_prototype(output, *images):
 	first.save(output)
 
 
+@cli
+def get_frame(*segments):
+	for path in segments:
+		segment = parse_segment_path(path)
+		filename = segment.start.strftime("%Y-%m-%dT-%H-%M-%S") + ".png"
+		with open(filename, "wb") as f:
+			for chunk in extract_frame([segment], segment.start):
+				common.writeall(f.write, chunk)
+		print(filename)
+
+
 def extract_segment(prototypes, segment):
 	# We haven't observed worse than 0.15 or so in the wild,
 	# and an all-black screen is identified as "1" with a score of 0.07.