PDFTextStripper character suppression
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Key: PDFBOX-662
URL: https://issues.apache.org/jira/browse/PDFBOX-662
Project: PDFBox
Issue Type: Bug
Components: Text extraction
Affects Versions: 1.0.0
Environment: any
Reporter: Mel Martinez
When parsing the file posted as an example for PDFBox-659, I noticed that
numerous characters were missing from the extracted text.
They are getting 'suppressed' in the
PDFTextStripper.processTextPosition(TextPosition) method in a section that is
meant to try to filter duplicate chars found in some MS Word - generated
documents.
The problem is that the filter is over-zealous (in the case of this document)
and matches real characters against other real characters in the text. Example
This is some text that has the letter 'e' in it multiple times.
The filter might match one of the later 'e's to an earlier 'e' incorrectly (for
example, the one at the end of 'some'), resulting in the extracted text:
This is some text that has the letter 'e' in it multiple tims.
.
>From what I can tell this is because it is using the raw, padded coordinates
>rather than resolved coordinates.
The example PDF document (see PDFBOX-659) has pages that use both positive and
negative raw coordinates that upon my cursory inspection don't always resolve
on the same offset point.
The suppression test logic compares textposition elements that seem to have
different offsets, possibly due to different amounts of padding. Thus the
'overlap' that it detects is wrong. Its not comparing apples to apples.
The document renders perfectly in Acrobat, so I believe we are not handling
the coordinates correctly.
A workaround is possible through suppressing the filtering by setting the
PDFTextStripper.setSuppressDuplicateOverlappingText(boolean)
attribute to false. But that is just hiding the fact that the logic is wrong.
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