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47bc734318
Some publishers generate pdfs with the watermarks inside the text of a page, in which case the object needs to be replaced. This deflates the object and uses plaintext instead. While this increases the size of the pdf, it is also effective for removing watermarks from the stream.
66 lines
2.1 KiB
Python
66 lines
2.1 KiB
Python
# -*- coding: utf-8 -*-
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"""
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pdfparanoia.eraser
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~~~~~~~~~~~~~~~
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Tools to erase things from pdfs by direct manipulation of the pdf format.
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"""
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def manipulate_pdf(content, objid, callback, *args):
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"""
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Iterates through a pdf looking for the object with the objid id. When the
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object is found, callback is called with a reference to the current list of
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output lines.
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"""
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outlines = []
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content = content.replace("\r\n", "\n")
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lines = content.split("\n")
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last_line = None
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skip_mode = False
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for line in lines:
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if not skip_mode:
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if last_line in ["endobj", "endobj ", None]:
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if line[-3:] == "obj" or line[-4:] == "obj " or " obj<<" in line[0:50]:
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if line.startswith(str(objid) + " "):
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skip_mode = True
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last_line = line
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callback(outlines, *args)
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continue
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outlines.append(line)
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elif skip_mode:
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if line == "endobj" or line == "endobj ":
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skip_mode = False
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last_line = line
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output = "\n".join(outlines)
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return output
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def remove_object_by_id(content, objid):
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"""
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Deletes an object from a pdf. Mostly streams and FlateDecode stuff.
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"""
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def _remove_object(outlines): pass
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output = manipulate_pdf(content, objid, _remove_object)
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return output
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def replace_object_with(content, objid, replacement):
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"""
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Replaces an object from a pdf. Mostly streams. This is useful for replacing
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an encoded object with a plaintext object.
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"""
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def _replace_object_with(outlines, details):
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objid = details["objid"]
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replacement = details["replacement"]
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output = str(objid) + " 0 obj\n"
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output += "<</Length " + str(len(replacement)+2) + ">>stream\n"
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output += replacement
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output += "\nendstream\nendobj\n"
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for line in output.split("\n"):
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outlines.append(line)
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output = manipulate_pdf(content, objid, _replace_object_with, {"objid": objid, "replacement": replacement})
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return output
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