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From Andreas Lehmkühler (JIRA) <j...@apache.org>
Subject [jira] Resolved: (PDFBOX-93) Error in FlateFilter?
Date Fri, 06 Feb 2009 15:19:59 GMT

     [ https://issues.apache.org/jira/browse/PDFBOX-93?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andreas Lehmkühler resolved PDFBOX-93.
--------------------------------------

       Resolution: Fixed
    Fix Version/s: 0.8.0-incubator

This issue was already solved in 2007.

> Error in FlateFilter?
> ---------------------
>
>                 Key: PDFBOX-93
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-93
>             Project: PDFBox
>          Issue Type: Bug
>             Fix For: 0.8.0-incubator
>
>
> [imported from SourceForge]
> http://sourceforge.net/tracker/index.php?group_id=78314&atid=552832&aid=1291763
> Originally submitted by yves_bussard on 2005-09-15 01:58.
> Hi Ben,
> While debugging a problem I had I found the following
> line in the method FlateFilter.decode():
> if (predictor==-1 || predictor == 1 && predictor == 10)
> This is on line 95. Shouldn't the && operator be a || ?
> cheers
> Yves
> [comment on SourceForge]
> Originally sent by thib_gc.
> Logged In: YES 
> user_id=736114
> I agree with reporter yves_bussard that the && in line 94 is
> highly likely supposed to be ||. Clearly, the three-boolean
> statement has no non-trivial meaning, even with parentheses.
> The Fifth Edition (PDF 1.6) states the following about the
> possible value of (what is in that Java code) the variable
> "predictor":
>  1  No prediction (the default value)
>  2  TIFF Predictor 2
>  10 PNG prediction (on encoding, PNG None on all rows)
>  11 PNG prediction (on encoding, PNG Sub on all rows)
>  12 PNG prediction (on encoding, PNG Up on all rows)
>  13 PNG prediction (on encoding, PNG Average on all rows)
>  14 PNG prediction (on encoding, PNG Paeth on all rows)
>  15 PNG prediction (on encoding, PNG optimum)
> (Table 3.8, page 52) The value 10 isn't very significant;
> though it flags the data as PNG, it declares that there is
> no prediction. The value 1 is the canonical declaration that
> there is no prediction. Thus it seems quite normal that -1,
> 1 and 10 (-1 being the default in the code) all go down the
> same code path.
> As it stands in 0.7.3, the "else" branch that start line 102
> never gets executed, yet it seems to deal with images. So
> while I don't have a sample file on hand, it would seem that
> some particular encodings of PNG images may trigger a
> problem by going down a path with no prediction even though
> they require a predictor function. (I don't know what the
> 0.7.4 code looks like.)
> [comment on SourceForge]
> Originally sent by yves_bussard.
> Logged In: YES 
> user_id=908162
> This line actually is not the source of my problem. I just
> stumbled over it. It is a logical problem (or I really need
> to start learning java again from scratch): How can a
> variable be equal to 1 AND 10. The line just doesn't make sense.
> [comment on SourceForge]
> Originally sent by yves_bussard.
> Logged In: YES 
> user_id=908162
> This line actually is not the source of my problem. I just
> stumbled over it. It is a logical problem (or I really need
> to start learning java again from scratch): How can a
> variable be equal to 1 AND 10. The line just doesn't make sense.
> [comment on SourceForge]
> Originally sent by benlitchfield.
> Logged In: YES 
> user_id=601708
> The predictor section of code was actually a contribution, so I 
> will need to take a little while to verify what is going on.  Can 
> you attach/upload a PDF that exhibits this issue?
> Ben

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