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<p class="MsoNormal"><span style="font-size:11.0pt">There are many different ways to add OCR’d text to a PDF, though one of the most common is use of “hidden text”, where the text is drawn using Text Render Mode 3. I don’t recall if Poppler exposes this information
in the public APIs, but it certainly has it in the graphic state internally.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Leonard<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">poppler <poppler-bounces@lists.freedesktop.org> on behalf of Stéphane Charette <stephanecharette@gmail.com><br>
<b>Date: </b>Friday, October 14, 2022 at 2:54 PM<br>
<b>To: </b>poppler@lists.freedesktop.org <poppler@lists.freedesktop.org><br>
<b>Subject: </b>[poppler] getting the text from PDF files<o:p></o:p></span></p>
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<p><strong><span style="font-size:10.5pt;font-family:"Calibri",sans-serif;color:black">EXTERNAL: Use caution when clicking on links or opening attachments.</span></strong><o:p></o:p></p>
<p><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Using libpoppler-cpp-dev 0.86.1 on Ubuntu to read PDF files. Works well.<br clear="all">
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">doc->create_page(idx) to get the page, then page->text_list() to get all the boxes. PDFs seem to either have text, or if it was a scan then I have an image with no text, and I fall back to other techniques
to read what I need.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">But...! Some fax machines and business scanners try to do OCR, and embeds the text results into the PDF. The quality of the OCR is poor, but when I attempt to extract the text, I do get back the expected
text boxes which leads me down the wrong path.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Is there anything in the way the text was added to the PDF that I can use as a hint that the text was added to the PDF after-the-fact, and not as part of the original PDF creation process? Something I can
use to determine if the text can be trusted? Reading up on things like Xref tables to get an understanding of the internals of PDF files so I can attempt to find a pattern between my "good" and "problematic" PDF files. Wondered if there was a way to see
if the text is part of the page itself, or if it was tacked on afterwards.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Thanks,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Stéphane<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">-- <o:p></o:p></span></p>
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<p class="MsoNormal" style="line-height:0%"><a href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fabout.me%2Fstephane.charette%3Fpromo%3Demail_sig%26utm_source%3Dproduct%26utm_medium%3Demail_sig%26utm_campaign%3Dedit_panel%26utm_content%3Dthumb&data=05%7C01%7Clrosenth%40adobe.com%7C929dbafc69344f80df8f08daae159382%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C638013704942713530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=8sHxTZ4vVD6XTu1Vro0Bjm%2Fl1lUVdXU6hLVgXqVG0Uw%3D&reserved=0" target="_blank"><span style="font-size:11.0pt;color:windowtext;text-decoration:none"><span style="color:blue;border:solid windowtext 1.0pt;padding:0in"><img border="0" width="105" height="70" style="width:1.0937in;height:.7291in" id="_x0000_i1026" src="cid:~WRD3845.jpg" alt="Image removed by sender."></span></span></a><span style="font-size:11.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;border:solid windowtext 1.0pt;padding:0in"><img border="0" width="1" height="1" style="width:.0104in;height:.0104in" id="_x0000_i1025" src="cid:~WRD3845.jpg" alt="Image removed by sender."></span><span style="font-size:11.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:13.5pt;font-family:Helvetica;color:#333333">Stéphane Charette<o:p></o:p></span></b></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fabout.me%2Fstephane.charette%3Fpromo%3Demail_sig%26utm_source%3Dproduct%26utm_medium%3Demail_sig%26utm_campaign%3Dedit_panel%26utm_content%3Dthumb&data=05%7C01%7Clrosenth%40adobe.com%7C929dbafc69344f80df8f08daae159382%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C638013704942713530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=8sHxTZ4vVD6XTu1Vro0Bjm%2Fl1lUVdXU6hLVgXqVG0Uw%3D&reserved=0" target="_blank"><span style="font-size:9.0pt;font-family:Helvetica;color:#2B82AD">about.me/stephane.charette</span></a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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