Detect actual charset encoding in UTF

问题

Need good tool to detect encoding of the strings using some kind of mapping or heuristic method.

For example String: áÞåàÐÝØÒ ÜÝÞÓÞ ßàØÛÞÖÕÝØÙ Java, ÜÞÖÝÞ ×ÐÝïâì Òáî ÔÞáâãßÝãî ßÐÜïâì

Expected: сохранив много приложений Java, можно занять всю доступную память

The encoding is "ISO8859-5". When I'am trying to detect it with the below libs the result is "UTF-8". It is obviously that string was saved in utf, but is there any heuristic way using symbols mapping to analyse the characters and match them with the correct encoding?

Used usual encoding detect libs:

- enca (aptitude install enca)
- chardet (aptitude install chardet)
- uchardet (aptitude install uchardet)
- http://tika.apache.org/
- http://npmjs.com/package/detect-encoding
- libencode-detect-perl
- http://www-archive.mozilla.org/projects/intl/UniversalCharsetDetection.html
- http://jchardet.sourceforge.net/
- http://grepcode.com/snapshot/repo1.maven.org/maven2/com.googlecode.juniversalchardet/juniversalchardet/1.0.3/
- http://lxr.mozilla.org/seamonkey/source/extensions/universalchardet/src/
- http://userguide.icu-project.org/
- http://site.icu-project.org

回答1:

You need to unwrap the UTF-8 encoding and then pass it to a character-encoding detection library.

If random 8-bit data is encoded into UTF-8 (assuming an identity mapping, i.e. a C4 byte is assumed to represent U+00C4, as is the case with ISO-8859-1 and its superset Windows 1252), you end up with something like

Source:  8F    0A 20 FE    65
Result:  C2 8F 0A 20 C3 BE 65

(because the UTF-8 encoding of U+008F is C2 8F, and U+00FE is C3 BE). You need to revert this encoding in order to obtain the source string, so that you can then identify its character encoding.

In Python, something like

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import chardet

mystery = u'áÞåàÐÝØÒ ÜÝÞÓÞ ßàØÛÞÖÕÝØÙ Java, ÜÞÖÝÞ ×ÐÝïâì Òáî ÔÞáâãßÝãî ßÐÜïâì'
print chardet.detect(mystery.encode('cp1252'))

Result:

{'confidence': 0.99, 'encoding': 'ISO-8859-5'}

On the Unix command line,

vnix$ echo 'áÞåàÐÝØÒ ÜÝÞÓÞ ßàØÛÞÖÕÝØÙ Java, ÜÞÖÝÞ ×ÐÝïâì Òáî ÔÞáâãßÝãî ßÐÜïâì' |
> iconv -t cp1252 | chardet
<stdin>: ISO-8859-5 (confidence: 0.99)

or iconv -t cp1252 file | chardet to decode a file and pass it to chardet.

(For this to work successfully at the command line, you need to have your environment properly set up for transparent Unicode handling. I am assuming that your shell, your terminal, and your locale are adequately configured. Try a recent Ubuntu Live CD or something if your regular environment is stuck in the 20th century.)

In the general case, you cannot know that the incorrectly applied encoding is CP 1252 but in practice, I guess it's going to be correct (as in, yield correct results for this scenario) most of the time. In the worst case, you would have to loop over all available legacy 8-bit encodings and try them all, then look at the one(s) with the highest confidence rating from chardet. Then, the example above will be more complex, too -- the mapping from legacy 8-bit data to UTF-8 will no longer be a simple identity mapping, but rather involve a translation table as well (for example, a byte F5 might correspond arbitrarily to U+0092 or whatever).

(Incidentally, iconv -l spits out a long list of aliases, so you will get a lot of fundamentally identical results if you use that as your input. But here is a quick ad-hoc attempt at fixing your slightly weird Perl script.

#!/bin/sh
iconv -l |
grep -F -v -e UTF -e EUC -e 2022 -e ISO646 -e GB2312 -e 5601 |
while read enc; do
    echo 'áÞåàÐÝØÒ ÜÝÞÓÞ ßàØÛÞÖÕÝØÙ Java, ÜÞÖÝÞ ×ÐÝïâì Òáî ÔÞáâãßÝãî ßÐÜïâì' |
    iconv -f utf-8 -t "${enc%//}" 2>/dev/null |
    chardet | sed "s%^[^:]*%${enc%//}%"
done |
grep -Fwive ascii -e utf -e euc -e 2022 -e None |
sort -k4rn

The output still contains a lot of chaff, but once you remove that, the verdict is straightforward.

It makes no sense to try any multi-byte encodings such as UTF-16, ISO-2022, GB2312, EUC_KR etc in this scenario. If you convert a string into one of these successfully, then the result will most definitely be in that encoding. This is outside the scope of the problem outlined above: a string converted from an 8-bit encoding into UTF-8 using the wrong translation table.

The ones which returned ascii definitely did something wrong; most of them will have received an empty input, because iconv failed with an error. In a Python script, error handling would be more straightforward.)

回答2:

The string

сохранив много приложений Java, можно занять всю доступную память

is encoded in ISO8859-5 as bytes

E1 DE E5 E0 D0 DD D8 D2 20 DC DD DE D3 DE 20 DF E0 D8 DB DE D6 D5 DD D8 D9 20 4A 61 76 61 2C 20 DC DE D6 DD DE 20 D7 D0 DD EF E2 EC 20 D2 E1 EE 20 D4 DE E1 E2 E3 DF DD E3 EE 20 DF D0 DC EF E2 EC

The string

áÞåàÐÝØÒ ÜÝÞÓÞ ßàØÛÞÖÕÝØÙ Java, ÜÞÖÝÞ ×ÐÝïâì Òáî ÔÞáâãßÝãî ßÐÜïâì

is encoded in ISO-8859-1 as bytes

E1 DE E5 E0 D0 DD D8 D2 20 DC DD DE D3 DE 20 DF E0 D8 DB DE D6 D5 DD D8 D9 20 4A 61 76 61 2C 20 DC DE D6 DD DE 20 D7 D0 DD EF E2 EC 20 D2 E1 EE 20 D4 DE E1 E2 E3 DF DD E3 EE 20 DF D0 DC EF E2 EC

Look familiar? They are the same bytes, just interpreted differently by different charsets.

Any tool that would look at these bytes would not be able to tell you the charset automatically, as they are perfectly valid bytes in both charsets. You would have to tell the tool which charset to use when interpreting the bytes.

Any tool that tells you this particular byte sequence is encoded as UTF-8 is wrong. These are NOT valid UTF-8 bytes.

来源：https://stackoverflow.com/questions/27832597/detect-actual-charset-encoding-in-utf

标签

encoding

utf-8

character-encoding