Scan and automatically OCR receipts, bills, letters, etc. without turning on your computer

I was looking for a solution to digitally archive incoming (paper) bills, receipts, letters, etc. to make them easily searchable (OCR). Ideally, this solutions would be as simply as putting a document on your scanner and pressing a button—done: the digitized document would be stored on a network drive. I really don’t like having to turn on your computer, opening up the scanner software, starting the OCR, saving the file, etc.

Existing Solutions

There are a few interesting scanning solutions out there, but I found them either too expensive or missing some functionalities. Here are some examples, they might work for you:

• Doxie Go: looks promising (“scan anywhere”), but I couldn’t figure out if you’d be able to scan directly to a network drive; also, it is sort of pricey (> 200 EUR for the Wifi version)
• Fujitsu ScanSnap iX500: even more expensive (close to 400 EUR)

Solution Based on NAS + All-In-One Scanner-Printer

In the end, I decided to use my existing NAS (a Synology DS213) to both OCR and store documents. I bought a HP Officejet Pro 8160 as scanner because it can directly scan to network drives—and priced at about 130 EUR it is cheaper than the other scanners (while being a printer and fax at the same time).

Usage

The work flow goes like this:

• Put a document on the scanner glass (or use the scanner’s document feeder)
• Using the scanner’s touch screen, select “scan to network” and the destination drive (pre-configured via the web interface)

What happens in the background:

• The scanner saves the document as JPG on a shared network folder on the NAS
• A script on the NAS is watching this shared folder:
  • Once a new scan appears, it runs OCR and saves the scan as searchable PDF
  • It also tries to extract a date (e.g., from an invoice) to append to the file name

Installation of OCR Package on the NAS

Setting up OCR was not as easy as I had hoped for, but worked out in the end. Here is a how-to:

• login via SSH on the Diskstation
• install the IPKG package manager (instructions)
• install tesseract-OCR from source (to get the latest version)
  • install GCC via package manager

    ipkg install gcc

  • install leptonica, autoconf, automake, libtool (use 2.4.5, 2.4.6 did not work) from source
  • install tesseract from source
    • run

      ./autogen.sh

    • dirty workaround to make it compile: in ccutils/helpers.h: put smaller numbers in lines 64 and 65 (e.g., 63641362 and 14426950)—I did not investigate, but using a different seed for the random generator does not seem to be critical for an OCR application…
    • fix pthread issue (original post)
      • backup the pthread libraries found in /opt/arm-none-linux-gnueabi/lib/

        mkdir /opt/arm-none-linux-gnueabi/lib_disabled
        mv /opt/arm-none-linux-gnueabi/lib/libpthread* \
           /opt/arm-none-linux-gnueabi/lib_disabled

      •  copy the pthread libraries found in /opt/lib

        cp /lib/libpthread.so.0 /opt/arm-none-linux-gnueabi/lib/
        cd /opt/arm-none-linux-gnueabi/lib/
        ln -s libpthread.so.0 libpthread.so
        ln -s libpthread.so.0 libpthread-2.5.so

    • run

      ./make
      ./make install

    • download tessdata to /usr/local/share/tessdata
    • edit /etc/profil and add

      export TESSDATA_PREFIX=/usr/local/share/tessdata/

• configure tesseract to also create text files (used for date extraction below) by editing /usr/local/share/tessdata/configs/pdf as follows

  tessedit_create_txt 1
  tessedit_create_pdf 1
  tessedit_pageseg_mode 1

• test with sample JPG file (this example uses a German dictionary)

  tesseract scan.jpg outfile -l deu /usr/local/share/tessdata/configs/pdf

Setting up Folder Watch

I’m using inotifywait to detect when new files are added to the watched folder. I created a shell script to start and stop watching. Note that everything is configured for German documents and German date format.

Additional Configuration Steps

• Configuring the scanner to scan to a specific shared network folder is straightforward using the scanner’s web interface.
• Likewise, sharing a folder from the NAS is straightforward using its excellent web interface.