update style-tranfer.ipynb

Makefile

@@ -10,6 +10,8 @@ BUILD=build
 PDFLATEX=pdflatex
 # the pointer to the bibilography engine (bibtex)
 BIBTEX=bibtex
+# the number of frames of interpolation to use in videos
+INTER_FRAMES=3
 
 # install Python dependencies in the requirements.txt
 install:
@@ -52,7 +54,7 @@ review_w_ref: build
 # Args:
 #   1: the name of the directory in the build directory to find frames in
 define frames_to_video
-	${PYTHON} frames_to_video.py build/$(1) build/$(1).mp4
+	${PYTHON} frames_to_video.py build/$(1) build/$(1).mp4 ${INTER_FRAMES}
 endef
 
 # make all the content reconstruction videos

frames_to_video.py

@@ -5,9 +5,30 @@
 from os import listdir
 
 
-# get the directory from the command line input
+def pairs(iterable):
+    """
+    Return a new iterable over sequential pairs in the given iterable.
+    i.e. (0,1), (1,2), ..., (n-2,n-1)
+    Args:
+        iterable: the iterable to iterate over the pairs of
+    Returns: a new iterator over the pairs of the given iterator
+    """
+    # lazily import tee from `itertools`
+    from itertools import tee
+    # split the iterator into 2 identical iterators
+    a, b = tee(iterable)
+    # retrieve the next item from the b iterator
+    next(b, None)
+    # zip up the iterators of current and next items
+    return zip(a, b)
+
+
+# the directory of png files to make into a video
 directory = argv[1]
+# the name of the video file to write
 video_name = argv[2]
+# the number of frames to use for interpolation
+interpolation_frames = int(argv[3])
 
 # get the frames from the given directory in sorted order
 frames = [filename for filename in listdir(directory) if '.png' in filename]
@@ -23,8 +44,19 @@
 out = cv2.VideoWriter(video_name, fourcc, 20.0, (width, height))
 
 # write the frames to the video file
-for frame in frames:
-	out.write(frame)
+for frame, next_frame in pairs(frames):
+    # write the current frame
+    out.write(frame)
+    # iterate over the number of interpolation frames
+    for i in range(1, interpolation_frames + 1):
+        # calculate a frame between current and next frames
+        w = i / interpolation_frames
+        mid_frame = cv2.addWeighted(frame, 1 - w, next_frame, w, 0)
+        # write this mid frame to the video
+        out.write(mid_frame)
+
+# the last frame still needs written
+out.write(frames[-1])
 
 # cleanup and release the video
 out.release()