Formwrapper and Pdfwrapper cannot fill image field

[73VW]

Hello there,

It seems that the package has difficulties identifying and filling image selection fields.

Here's an example of file with such field: https://www.liguepulmonaire.ch/sites/default/files/documents/verordnungsformular_4f.pdf

That's a prescription template.

It detects the field as Checkbox but the field doesn't have the /AP/D properties.

Here's the value of the widget:

{'/A': IndirectObject(665, 0, 140288380589648), '/DA': '/SyntaxLTStd-Roman 10 Tf 0 g', '/F': 4, '/FT': '/Btn', '/Ff': 65536, '/MK': {'/IF': {'/FB': True}, '/TP': 1}, '/P': IndirectObject(485, 0, 140288380589648), '/Rect': [382.767, 123.965, 541.868, 215.683], '/Subtype': '/Widget', '/T': 'ImageSign', '/Type': '/Annot'}

I will try to reverse engineer the content of the field just as I have done in #559 in order to try to fix this but I guess that won't be an easy trick.

[73VW]

The wrong detection seems to come from these lines:
https://github.com/chinapandaman/PyPDFForm/blob/master/PyPDFForm/patterns.py#L25-L26

Which catches all buttons

[chinapandaman]

So image field is not a widget type that the library supports. I don't think it's explicitly stated in the docs but I can add it later if it ever causes confusions.

The reasons is simple, I do not know what pattern precisely characterizes a widget as an image field. If this ever comes clear someday I can make PdfWrapper support it. This is not hard given it already supports signature field and draw_image. I don't think there will ever be a day that FormWrapper supports image field because I don't think I can feed an image file stream into a image widget even if I know it's an image field. This is the same reason why FormWrapper doesn't support signature field and I made that very clear in the docs.

[73VW]

Hey @chinapandaman,

Indeed, I've searched on the internet and didn't find a standard regarding image fields. I totally understand that it will be hard to implement a standard out of it.

If you wish, I can try to support the signature field in FormWrapper first.

[chinapandaman]

You are more than welcomed to try getting the signature field to work for FormWrapper! If it helps at all this is by far the best resource I have been referring to. It's the ISO 32000 PDF standard document and chapter 12.7.4 (page 447) is where most information about form widgets is at.

[chinapandaman]

Hey @73VW, it's been a little over a week now. Do you mind if I close this issue? When you have something we could always open another one.

[chinapandaman]

Hey, so I spent today looking into this a bit more. When I compared your PDF with a PDF form with image field of mine, I noticed something that both PDF's image widgets share in common. Both image widgets have an /A property and it has three sub-properties:

• /Type with a value /Action
• /S with a value /JavaScript
• /JS with a value event.target.buttonImportIcon();

I believe the /JS property's script is what get's executed when rendering the image field widget. So I googled event.target.buttonImportIcon(); and all the results I got indicate something related to PDF form's image field.

So I think this is a good enough evidence for identifying image field and I went ahead and wrote this PR. I added your PDF form as a test case and it seemed to work fine.

Anyway, the changes are released. Give v1.4.21 a try and tell me what you think. Docs are also updated.