glitterpos_util.py

"""a handful of utility functions used by GlitterPOS."""
import math
import time

# https://gist.githubusercontent.com/jeromer/2005586/raw/5456a9386acce189ac6cc416c42e9c4b560a633b/compassbearing.py
def compass_bearing(pointA, pointB):
    """
    Calculates the bearing between two points.

    The formulae used is the following:
        θ = atan2(sin(Δlong).cos(lat2),
                  cos(lat1).sin(lat2) − sin(lat1).cos(lat2).cos(Δlong))

    :Parameters:
      - `pointA: The tuple representing the latitude/longitude for the
        first point. Latitude and longitude must be in decimal degrees
      - `pointB: The tuple representing the latitude/longitude for the
        second point. Latitude and longitude must be in decimal degrees

    :Returns:
      The bearing in degrees

    :Returns Type:
      float
    """
    if (type(pointA) != tuple) or (type(pointB) != tuple):
        raise TypeError("Only tuples are supported as arguments")

    lat1 = math.radians(pointA[0])
    lat2 = math.radians(pointB[0])

    diffLong = math.radians(pointB[1] - pointA[1])

    x = math.sin(diffLong) * math.cos(lat2)
    y = math.cos(lat1) * math.sin(lat2) - (math.sin(lat1)
            * math.cos(lat2) * math.cos(diffLong))

    initial_bearing = math.atan2(x, y)

    # Now we have the initial bearing but math.atan2 return values
    # from -180° to + 180° which is not what we want for a compass bearing
    # The solution is to normalize the initial bearing as shown below
    initial_bearing = math.degrees(initial_bearing)
    compass_bearing = (initial_bearing + 360) % 360

    return compass_bearing

def bearing_to_pixel(bearing, count=16):
    # Subtract from count since the neopixel ring runs counterclockwise:
    pixel = count - int(round((bearing / 360) * count))
    if pixel == count:
      return 0
    return pixel

def map_range(x, in_min, in_max, out_min, out_max):
    """
    Maps a number from one range to another.
    :return: Returns value mapped to new range
    :rtype: float
    """
    mapped = (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min
    if out_min <= out_max:
        return max(min(mapped, out_max), out_min)

    return min(max(mapped, out_max), out_min)

def timestamp():
    """print a human-readable timestamp"""
    timestamp = time.localtime()
    return '{}/{}/{} {:02}:{:02}:{:02}'.format(
        timestamp.tm_year,
        timestamp.tm_mon,
        timestamp.tm_mday,
        timestamp.tm_hour,
        timestamp.tm_min,
        timestamp.tm_sec
    )