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https://issues.apache.org/jira/browse/TIKA-2771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16672520#comment-16672520
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Hans Brende commented on TIKA-2771:
-----------------------------------
Just had another thought: when the input filter is enabled, it strips
everything within "<" and ">" brackets (i.e. 0x3C and 0x3E), correct? But doing
so *presupposes* an ASCII-compatible encoding! Thus, if a significant number of
matching "<" and ">" symbols are found, you *already* know it can't be IBM500!
("<" and ">" in IBM500 are 0x4C and 0x6E, respectively.) I assume you could
extend this logic to other ASCII-incompatible charsets as well.
> enableInputFilter() wrecks charset detection for some short html documents
> --------------------------------------------------------------------------
>
> Key: TIKA-2771
> URL: https://issues.apache.org/jira/browse/TIKA-2771
> Project: Tika
> Issue Type: Bug
> Components: detector
> Affects Versions: 1.19.1
> Reporter: Hans Brende
> Priority: Critical
>
> When I try to run the CharsetDetector on
> http://w3c.github.io/microdata-rdf/tests/0065.html I get the very strange
> most confident result of "IBM500" with a confidence of 60 when I enable the
> input filter, *even if I set the declared encoding to UTF-8*.
> This can be replicated with the following code:
> {code:java}
> CharsetDetector detect = new CharsetDetector();
> detect.enableInputFilter(true);
> detect.setDeclaredEncoding("UTF-8");
> detect.setText(("<!DOCTYPE html>\n" +
> "<div>\n" +
> " <div itemscope itemtype=\"http://schema.org/Person\"; id=\"amanda\"
> itemref=\"a b\"></div>\n" +
> " <p id=\"a\">Name: <span itemprop=\"name\">Amanda</span></p>\n" +
> " <p id=\"b\" itemprop=\"band\">Jazz Band</p>\n" +
> "</div>").getBytes(StandardCharsets.UTF_8));
> Arrays.stream(detect.detectAll()).forEach(System.out::println);
> {code}
> which prints:
> {noformat}
> Match of IBM500 in fr with confidence 60
> Match of UTF-8 with confidence 57
> Match of ISO-8859-9 in tr with confidence 50
> Match of ISO-8859-1 in en with confidence 50
> Match of ISO-8859-2 in cs with confidence 12
> Match of Big5 in zh with confidence 10
> Match of EUC-KR in ko with confidence 10
> Match of EUC-JP in ja with confidence 10
> Match of GB18030 in zh with confidence 10
> Match of Shift_JIS in ja with confidence 10
> Match of UTF-16LE with confidence 10
> Match of UTF-16BE with confidence 10
> {noformat}
> Note that if I do not set the declared encoding to UTF-8, the result is even
> worse, with UTF-8 falling from a confidence of 57 to 15.
> This is screwing up 1 out of 84 of my online microdata extraction tests over
> in Any23 (as that particular page is being rendered into complete gibberish),
> so I had to implement some hacky workarounds which I'd like to remove if
> possible.
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