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https://issues.apache.org/jira/browse/PDFBOX-5623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17738151#comment-17738151
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Lionel Fradin commented on PDFBOX-5623:
---------------------------------------

[~mkl] ,

Thank you for your comment. Your analysis, and in particular
{quote}The second one is created by some unknown tool which has added two 
signature fields on the last page of the document and changed the *SigFlags* 
entry from {{1}} to {{{}3{}}}. Its *Index* entry is broken: {{[ 6788 1 6789 1 
6790 1 6791 1 5327 1 6485 1 ]}}
{quote}
helped identify the component causing the broken index. This custom component 
will be fixed so that future pdfs will become more standard-abiding. The pdfbox 
fix, on the other hand, will help reading the thousands files that were 
created, and signed, with the broken index. 

> Signature Image not Rendered starting with PDFBox 2.0.23 + patch provided
> -------------------------------------------------------------------------
>
>                 Key: PDFBOX-5623
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-5623
>             Project: PDFBox
>          Issue Type: Bug
>          Components: Rendering
>    Affects Versions: 2.0.23, 3.0.0 PDFBox
>         Environment: Java 8, Windows 10 and Ubuntu 22
>            Reporter: Lionel Fradin
>            Assignee: Andreas Lehmkühler
>            Priority: Major
>         Attachments: 
> Fixing_the_problem_when_the_COSArray_is_not_sorted_in_increasing_order_.patch,
>  PDFBOX-issue-rendering-signature.pdf, pdfbox22-page9-br.jpg, 
> pdfbox23-page9-br.jpg
>
>
> We have an online service where our customers post their PDF files so that we 
> can render them. 
> One of our customer noticed recently that one of its signed document did not 
> show the image associated with the signature. They gave me the right to share 
> this document and you will find it attached 
> ([^PDFBOX-issue-rendering-signature.pdf]).
> The problem is in the last page, page 9. The issue can easily be reproduced 
> using pdfbox-app-2.0*.jar PDFToImage.
> Result with pdfbox 2.0.22 is:
> !pdfbox22-page9-br.jpg!
> Result with pdfbox 2.0.23 or later is:
> !pdfbox23-page9-br.jpg!
> The regression was introduced with commit (seen in git) 
> [f34a33824c4363b9b683245cb582328dc92b79ca|https://github.com/apache/pdfbox/commit/f34a33824c4363b9b683245cb582328dc92b79ca],
>  dated 2021-03-02 07:12:11+0000. The associated ticket was PDFBOX-5112.
> The issue is in PDFXrefStreamParser's ObjectNumbers constructor, as it 
> assumes that the COSInteger objects in the COSArray are necessarily sorted. 
> In the case of the attached pdf, they are not, and this causes the parser to 
> abort browsing the array too soon.
> I have a patch for that on branch 2.0: 
> [^Fixing_the_problem_when_the_COSArray_is_not_sorted_in_increasing_order_.patch]
> With this patch the image is created successfully. However, there are warning 
> that appear, that did not exist in version 2.0.22:
> {noformat}
> Jun 16, 2023 5:18:29 PM org.apache.pdfbox.pdfparser.COSParser findObjectKey
> WARNING: found wrong object number. expected [6789] found [6791]
> Jun 16, 2023 5:18:29 PM org.apache.pdfbox.pdfparser.COSParser findObjectKey
> WARNING: found wrong object number. expected [6790] found [5327]
> Jun 16, 2023 5:18:29 PM org.apache.pdfbox.pdfparser.COSParser findObjectKey
> WARNING: found wrong object number. expected [6791] found [6485]
> Jun 16, 2023 5:18:29 PM org.apache.pdfbox.pdfparser.COSParser findObjectKey
> WARNING: found wrong object number. expected [6485] found [6789]
> {noformat}
> There may be additional fixes to be made in order to fully support this PDF. 
> I did not have time to investigate, and also my knowledge of the codebase if 
> fairly limited. So help would be appreciated here.
> Thanks.



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