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Posted to dev@pdfbox.apache.org by "Andre (Jira)" <ji...@apache.org> on 2022/10/18 09:30:00 UTC
[jira] [Updated] (PDFBOX-5528) PDF/UA: Add marked content sections when flattening acro forms
[ https://issues.apache.org/jira/browse/PDFBOX-5528?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Andre updated PDFBOX-5528:
--------------------------
Description:
We need to support PDF/UA compliant documents to some extent. I noticed that when we take a PDF/UA compliant PDF document and flatten it via PDAcroForm#flatten, the resulting output is not PDF/UA compliant anymore.
After a little bit of research, the problem is that PDFBox creates /DO operators with paths representing the appearance of the form fields. According to the PDF/UA standard, such paths need to be enclosed in marked content sections (BMC ... EMC, BDC ... EMC, see attached images)
By copying some code from AcroForm#flatten and adding contentStream.beginMarkedContent and contentStream.endMarkedContent myself, I can workaround the problem, but that's less than ideal, it would be great if this could be included in PDFBox.
{code:java}
final var dict = new COSDictionary();
dict.setLong(COSName.MCID, mcid);
dict.setItem(COSName.BBOX, bBox);
dict.setItem(COSName.TYPE, COSName.BACKGROUND);
final var propList = PDPropertyList.create(dict);
contentStream.beginMarkedContent(COSName.ARTIFACT, propList);
contentStream.saveGraphicsState();
// see https://stackoverflow.com/a/54091766/1729265 for an explanation
// of the steps required
// this will transform the appearance stream form object into the rectangle of the
// annotation bbox and map the coordinate systems
final var transformationMatrix = pdfbox_resolveTransformationMatrix(form, annotation, appearanceStream);
contentStream.transform(transformationMatrix);
contentStream.drawForm(fieldObject);
contentStream.restoreGraphicsState();
contentStream.endMarkedContent();
{code}
was:
We need to support PDF/UA compliant documents to some extent. I noticed that when we take a PDF/UA compliant PDF document and flatten it via PDAcroForm#flatten, the resulting output is not PDF/UA compliant anymore.
After a little bit of research, the problem is that PDFBox creates /DO operators with paths representing the appearance of the form fields. According to the PDF/UA standard, such paths need to be enclosed in marked content sections (BMC ... EMC, BDC ... EMC, see attached images)
By copying some code from AcroForm#flatten and adding contentStream.beginMarkedContent and contentStream.endMarkedContent myself, I can workaround the problem, but that's less than ideal, it would be great if this could be included in PDFBox.
<pre>
final var dict = new COSDictionary();
dict.setLong(COSName.MCID, mcid);
dict.setItem(COSName.BBOX, bBox);
dict.setItem(COSName.TYPE, COSName.BACKGROUND);
final var propList = PDPropertyList.create(dict);
contentStream.beginMarkedContent(COSName.ARTIFACT, propList);
contentStream.saveGraphicsState();
// see https://stackoverflow.com/a/54091766/1729265 for an explanation
// of the steps required
// this will transform the appearance stream form object into the rectangle of the
// annotation bbox and map the coordinate systems
final var transformationMatrix = pdfbox_resolveTransformationMatrix(form, annotation, appearanceStream);
contentStream.transform(transformationMatrix);
contentStream.drawForm(fieldObject);
contentStream.restoreGraphicsState();
contentStream.endMarkedContent();
</pre>
> PDF/UA: Add marked content sections when flattening acro forms
> --------------------------------------------------------------
>
> Key: PDFBOX-5528
> URL: https://issues.apache.org/jira/browse/PDFBOX-5528
> Project: PDFBox
> Issue Type: Improvement
> Components: AcroForm
> Reporter: Andre
> Priority: Minor
> Attachments: correct.png, wrong.png
>
>
> We need to support PDF/UA compliant documents to some extent. I noticed that when we take a PDF/UA compliant PDF document and flatten it via PDAcroForm#flatten, the resulting output is not PDF/UA compliant anymore.
> After a little bit of research, the problem is that PDFBox creates /DO operators with paths representing the appearance of the form fields. According to the PDF/UA standard, such paths need to be enclosed in marked content sections (BMC ... EMC, BDC ... EMC, see attached images)
> By copying some code from AcroForm#flatten and adding contentStream.beginMarkedContent and contentStream.endMarkedContent myself, I can workaround the problem, but that's less than ideal, it would be great if this could be included in PDFBox.
>
> {code:java}
> final var dict = new COSDictionary();
> dict.setLong(COSName.MCID, mcid);
> dict.setItem(COSName.BBOX, bBox);
> dict.setItem(COSName.TYPE, COSName.BACKGROUND);
> final var propList = PDPropertyList.create(dict);
> contentStream.beginMarkedContent(COSName.ARTIFACT, propList);
> contentStream.saveGraphicsState();
> // see https://stackoverflow.com/a/54091766/1729265 for an explanation
> // of the steps required
> // this will transform the appearance stream form object into the rectangle of the
> // annotation bbox and map the coordinate systems
> final var transformationMatrix = pdfbox_resolveTransformationMatrix(form, annotation, appearanceStream);
> contentStream.transform(transformationMatrix);
> contentStream.drawForm(fieldObject);
> contentStream.restoreGraphicsState();
> contentStream.endMarkedContent();
>
> {code}
>
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