36 lines
1.2 KiB
Python
36 lines
1.2 KiB
Python
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# This function is free of any dependencies.
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# source: https://github.com/mgd722/decode-google-maps-polyline
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def decode_polyline(polyline_str):
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'''Pass a Google Maps encoded polyline string; returns list of lat/lon pairs'''
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index, lat, lng = 0, 0, 0
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coordinates = []
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changes = {'latitude': 0, 'longitude': 0}
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# Coordinates have variable length when encoded, so just keep
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# track of whether we've hit the end of the string. In each
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# while loop iteration, a single coordinate is decoded.
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while index < len(polyline_str):
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# Gather lat/lon changes, store them in a dictionary to apply them later
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for unit in ['latitude', 'longitude']:
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shift, result = 0, 0
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while True:
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byte = ord(polyline_str[index]) - 63
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index+=1
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result |= (byte & 0x1f) << shift
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shift += 5
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if not byte >= 0x20:
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break
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if (result & 1):
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changes[unit] = ~(result >> 1)
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else:
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changes[unit] = (result >> 1)
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lat += changes['latitude']
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lng += changes['longitude']
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coordinates.append((lat / 100000.0, lng / 100000.0))
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return coordinates
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