![]() Regardless of the order in which you pass these options, OCRmyPDF will always apply them in this order: ![]() You will want to review each page to ensure that unpaper did not remove something important. clean-final uses unpaper to clean up pages before OCR and inserts the page into the final output. This makes it less likely that OCR will try to find text in background noise. clean uses unpaper to clean up pages before OCR, but does not alter the final output. deskew will correct pages were scanned at a skewed angle by rotating them back into place. This should not be used on documents that contain color photos as it may remove them. remove-background attempts to detect and remove a noisy background from grayscale or color images. rotate-pages attempts to determine the correct orientation for each page and rotates the page if necessary. We’ve included the text from the documentation in the list below: According to the official documentation, there are five different options. It supports multiple options for this purpose. Image ProcessingĪs mentioned earlier, OCRmyPDF can perform some image processing on each page of a PDF, if required. Follow these instructions to figure out how to do so. You might be required to install additional language packs before you can use them with OCRmyPDF. You can take a look at the Tesseract documentation to determine if it supports your required language. Tesseract (the OCR engine used by OCRmyPDF under the hood) supports quite a few different languages. Install OCRmyPDF using the following command on Ubuntu- or Debian-based systems: You can use Tesseract directly, but in doing so, you’ll miss out on these benefits provided by OCRmyPDF. OCRmyPDF also does some post-processing to ensure that the output is consistent and error-free. This preprocessing includes deskewing, noise removal, and cleaning up files to ensure the OCR engine can read the text accurately. OCRmyPDF is a wrapper around Tesseract that does some preprocessing on PDF files before running OCR on them. This next section will go into details on how to OCR a PDF on Linux with an open source library. How to OCR a PDF on Linux Using an Open Source Library The open source library you’ll use is OCRmyPDF, which is a multi-platform tool for running OCR on PDF files, and it’s based on the open source OCR engine Tesseract. ![]() It also covers how to use PSPDFKit Processor for more advanced OCR use cases. ImageMagik utilities: There are other questions on the SuperUser site about using ImageMagik that you might use to help you do the conversion.In this tutorial, you’ll learn how to OCR a PDF in Linux using an open source solution. Gs -SDEVICE=tiffg4 -r600圆00 -sPAPERSIZE=letter -sOutputFile=filename_%04d.tif -dNOPAUSE -dBATCH - filename Gs: The below command should convert multipage pdf to individual tiff files. (i.e I couldn't find a linux pdf2text converter that does OCR). You might also find the pdf toolkit of use.Ī full list of pdf software here on wikipedia.Įdit: Since you do need OCR capabilities, I think you'll have to try a different tack. If it's not on your machine, you'll have to install the poppler-utils package sudo apt-get install poppler-utils For example, it does not retain any PDF metadata. Please note that the above script is very rudimentary. Gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile="$output" "$tmpdir"/page-*.pdf Hocr2pdf -i "$page" -o "$base.pdf" < "$base.html" # OCR each page individually and convert into PDFĬuneiform -f hocr -o "$base.html" "$page" Gs -SDEVICE=tiffg4 -r300x300 -sOutputFile="$tmpdir/page-%04d.tiff" -dNOPAUSE -dBATCH - "$input" # extract images of the pages (note: resolution hard-coded) # Run OCR on a multi-page PDF file and create a new pdf with the Sadly, the program does not appear to support creating multi-page PDFs, so you might have to create a script to handle them: #!/bin/bash I have used hocr2pdf to recreate PDFs out of the original image-only PDFs and OCR results. This way you can create "searchable" PDFs from which you can copy text. The nice thing about it is that it can output position information for the OCR text in hOCR format, so that it becomes possible to put the text back in in the correct position in a hidden layer of a PDF file. While it appears to be essentially undocumented apart from a brief README file, I've found the OCR results quite good. Be sure to have the ImageMagick C++ libraries installed to have support for essentially any input image format (otherwise it will only accept BMP). ![]() No binary packages seem to be available, so you need to build it from source. I have had success with the BSD-licensed Linux port of Cuneiform OCR system.
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