improve frame2time helper function

turn return value into np.timedelta64
calculate timevalue by pd.Timedelta instead of divmod

itten/helpers.py

@@ -2,6 +2,7 @@
 # -*- coding: utf-8 -*-
 
 import numpy as np
+import pandas as pd
 import math
 
 
@@ -56,10 +57,20 @@ def time2framenr(time, fps=4):
     return in_sec *  fps
 
 
-def timelabels(val, pos):
-    min, sec = divmod(int(val), 60)
-    timelabel = "{0}:{1:02d}".format(min, sec)
-    return timelabel
+def frame2time(val, fps=4):
+    """transforms framenumbers into timecodes
+    
+    Arguments:
+        val {int} -- number of frame in the movie
+        fps {int} -- time interval by which frames were extracted from the movie
+    
+    Returns:
+        np.datetime64 -- timecode of the frame in the movie
+    """
+
+    val = round(val/fps)  # scale frame number to the unit of 1 sec
+    tstmp = pd.Timedelta(val, unit='s')
+    return tstmp
 
 def luminance(img):
     """Creates an array of luminance value for each pixel of an image