1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
package Travel::Status::DE::HAFAS::Polyline;
use strict;
use warnings;
use 5.014;
# Adapted from code by Slaven Rezic
#
# Copyright (C) 2009,2010,2012,2017,2018 Slaven Rezic. All rights reserved.
# This package is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# Mail: slaven@rezic.de
# WWW: http://www.rezic.de/eserte/
use parent 'Exporter';
our @EXPORT_OK = qw(decode_polyline);
our $VERSION = '5.02';
# Translated this php script
# <http://unitstep.net/blog/2008/08/02/decoding-google-maps-encoded-polylines-using-php/>
# to perl
sub decode_polyline {
my ($encoded) = @_;
my $length = length $encoded;
my $index = 0;
my @points;
my $lat = 0;
my $lng = 0;
while ( $index < $length ) {
# The encoded polyline consists of a latitude value followed
# by a longitude value. They should always come in pairs. Read
# the latitude value first.
for my $val ( \$lat, \$lng ) {
my $shift = 0;
my $result = 0;
# Temporary variable to hold each ASCII byte.
my $b;
do {
# The `ord(substr($encoded, $index++))` statement returns
# the ASCII code for the character at $index. Subtract 63
# to get the original value. (63 was added to ensure
# proper ASCII characters are displayed in the encoded
# polyline string, which is `human` readable)
$b = ord( substr( $encoded, $index++, 1 ) ) - 63;
# AND the bits of the byte with 0x1f to get the original
# 5-bit `chunk. Then left shift the bits by the required
# amount, which increases by 5 bits each time. OR the
# value into $results, which sums up the individual 5-bit
# chunks into the original value. Since the 5-bit chunks
# were reversed in order during encoding, reading them in
# this way ensures proper summation.
$result |= ( $b & 0x1f ) << $shift;
$shift += 5;
}
# Continue while the read byte is >= 0x20 since the last
# `chunk` was not OR'd with 0x20 during the conversion
# process. (Signals the end)
while ( $b >= 0x20 );
# see last paragraph of "Integer Arithmetic" in perlop.pod
use integer;
# Check if negative, and convert. (All negative values have the last bit
# set)
my $dtmp
= ( ( $result & 1 ) ? ~( $result >> 1 ) : ( $result >> 1 ) );
# Compute actual latitude (resp. longitude) since value is
# offset from previous value.
$$val += $dtmp;
}
# The actual latitude and longitude values were multiplied by
# 1e5 before encoding so that they could be converted to a 32-bit
# integer representation. (With a decimal accuracy of 5 places)
# Convert back to original values.
push(
@points,
{
lat => $lat * 1e-5,
lon => $lng * 1e-5
}
);
}
return @points;
}
1;
|
