Sebastian Holzki created PDFBOX-5580:
----------------------------------------
Summary: PDFTextStripperByArea ignores text for overlapping areas
(regions) when suppressing duplicate overlapping text
Key: PDFBOX-5580
URL: https://issues.apache.org/jira/browse/PDFBOX-5580
Project: PDFBox
Issue Type: Bug
Components: Text extraction
Affects Versions: 2.0.27
Reporter: Sebastian Holzki
Attachments: test.pdf
h3. Problem
Recently we encountered duplicate texts in our clients PDF documents which are
typically created by applications to simulate some kind of bold text when no
bold variant of a font is available. Fortunately, PDFBox's
PDFTextStripperByArea has some logic to ignore exact duplicates at the same
positions for these situations (which is inherited from the normal
PDFTextStripper). So we changed from setSuppressDuplicateOverlappingText(false)
to true.
But we encountered that texts for multiple regions are not extracted correctly
in this case when some special conditions are met:
When using multiple regions which overlap each other and would provide exactly
the same text, the first region text is extracted correctly but any following
region with same text remains empty.
We believe this is a bug due to duplicate suppression not being respected
correctly in PDFTextStripperByArea.
h3. Possible cause
While investigating this problem we found that PDFTextStripperByArea swaps
charactersByArticle for multiple regions and interprets a single page multiple
times (once for each region). In PDFTextStripper a private HashMap
characterListMapping keeps track of possible duplicate symbols with their
positions. The HasMap is not being reset after each region extraction which
leads to characters being ignored for subsequent areas.
Since the HashMap is private we were not able to subclass and customize
PDFTextStripperByArea with some adjusted behavior to test this finding.
h3. Workaround
When extracting regions one at a time for every page everything works fine. We
currently don't see any performance disadvantages.
h3. Reproduction
The attached PDF file does not actually include duplicate overlapping text
which is actually not needed to reproduce the issue.
{code:java}
try (final PDDocument doc = PDDocument.load(new File("C:\\Source\\test.pdf"))) {
final PDFTextStripperByArea stripper = new PDFTextStripperByArea();
stripper.setSuppressDuplicateOverlappingText(true);
stripper.setPageEnd("");
final Rectangle2D areaA = new Rectangle2D.Double(45, 319, 124, 19);
final Rectangle2D areaB = new Rectangle2D.Double(43, 319, 130, 19);
stripper.addRegion("A", areaA);
stripper.addRegion("B", areaB);
stripper.extractRegions(doc.getPage(0));
System.out.println("A: " + stripper.getTextForRegion("A"));
System.out.println("B: " + stripper.getTextForRegion("B"));
} {code}
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@pdfbox.apache.org
For additional commands, e-mail: dev-h...@pdfbox.apache.org
