extract_form_text.rst

.. testsetup::

  from pdfreader import SimplePDFViewer
  import pkg_resources, os.path
  samples_dir = pkg_resources.resource_filename('doc', 'examples/pdfs')
  file_name = os.path.join(samples_dir, 'example-form.pdf')

How to parse PDF Forms

In most cases texts come within page binary content streams and can be extracted as in :ref:`tutorial-texts` and :ref:`examples-parse-texts`.

There is one more place where text data can be found: page forms. Form is a special subtype of XObject which is a part of page resources, and can be referenced from page by do command.

You may think of Form as of "small subpage" that is stored aside main content.

Have a look at one :download:`PDF form <pdfs/example-form.pdf>`.

Let's open the document and get the 1st page.

>>> from pdfreader import SimplePDFViewer
>>> fd = open(file_name, "rb")
>>> viewer = SimplePDFViewer(fd)

And now, let's try to locate a string, located under the section B.3 SOC (ONET/OES) occupation title

>>> viewer.render()
>>> plain_text = "".join(viewer.canvas.strings)
>>> "Farmworkers and Laborers" in plain_text
False

Apparently, the texts typed into the form are in some other place. They are in Form XObjects, listed under page resources. The viewer puts them on canvas:

>>> sorted(list(viewer.canvas.forms.keys()))
['Fm1', 'Fm10', 'Fm11', 'Fm12', 'Fm13', 'Fm14',...]

As Form is a kind of "sub-document" every entry in viewer.canvas.forms dictionary maps to :class:`~pdfreader.viewer.SimpleCanvas` instance:

>>> form9_canvas = viewer.canvas.forms['Fm9']
>>> "".join(form9_canvas.strings)
'Farmworkers and Laborers, Crop, Nursery, and Greenhouse'

Here we are!

More on PDF Form objects: see sec. 8.10