[PDFBOX-4531] Extraction of Arabic PDF has incorrect ordering of normalized ligatures

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.15
• Fix Version/s: 2.0.28, 3.0.0 PDFBox
• Component/s: Text extraction
• Labels: Arabic regression
• Assignee: Tilman Hausherr
• Reporter: Tilman Hausherr
• Created: 30/Apr/19 09:04
• Updated: 13/Apr/23 14:54
• Resolved: 26/Feb/23 09:05

Description

As reported by Elias Peterson in the mailing list:

I think I'm seeing some issues concerning the handling of the Arabic lam-with-alef ligature. I'm attempting to process the PDF here:
https://www.rand.org/content/dam/rand/pubs/perspectives/PE100/PE122/RAND_PE122z1.arabic.pdf

When I run the ExtractText command with 2.0.15 I get the following:
$ java -jar pdfbox-app-2.0.15.jar ExtractText -encoding UTF-8 RAND_PE122z1.arabic.pdf output.txt
$ head output.txt
C O R P O R A T I O N
منظور تحليلي
رؤى خبير بشأن قضايا السياسات اآلنية
االتفاق مع إيران
األيام التي تلي
...

The issue being with the last two lines in the above snippet where my understanding is that the ligature لا was normalized but that the two letters that compose it are in the wrong order. I was thinking that PDFBOX-684 sounded similar, and running the same PDF through 1.8.16 I see the ligature is normalized in the way I think is expected (although the interspersed English-language words are backwards here).

$ java -jar pdfbox-app-1.8.16.jar ExtractText -encoding UTF-8 RAND_PE122z1.arabic.pdf output.txt
...
$ head output.txt
N O I T A R O P R O C
منظور تحليلي
رؤى خبير بشأن قضايا السياسات الآنية
الاتفاق مع إيران
الأيام التي تلي
...

Issue Links

• relates to: PDFBOX-4481 Text extraction error with Thai combined glyph depending on space after it
• relates to: PDFBOX-684 Incorrect ordering of compound Arabic glyphs
• links to: GitHub Pull Request #154
• links to: GitHub Pull Request #156