scan2drive

scan2drive is a Go program (with a web interface) for scanning, converting and uploading physical documents to Google Drive. The author runs scan2drive as a gokrazy appliance on a Raspberry Pi 4.

During the conversion step, scan2drive skips empty pages and converts the rest from multi-megabyte JPEGs into a kilobyte-sized PDF. This allows you to use Google Drive’s OCR-based full text search.

Both the originals and the converted PDF are uploaded to Google Drive, so that you can enjoy full text search but still have the full-quality originals just in case.

In comparison to the native Google Drive connectivity which some document scanner vendors provide, scan2drive has these main advantages:

scan2drive integrates with the scan button of your document scanner. You press one button and your documents will end up on Google Drive. Other solutions require you to use a mobile app or software on your PC.
scan2drive is self-hosted and depends only on Google Drive being available, not the scanner vendor’s cloud integration service. Many vendors send documents into their own clouds and then to Google Drive. You are welcome to archive the scan directory of scan2drive to other places you see fit, in case there are any issues with Google Drive.
scan2drive converts the scanned documents into a PDF which is small enough to be full text indexed by Google Drive, but it also retains the original JPEGs in case you need them.

Project status and vision

Currently, there are a number of open issues and not all functionality might work well. Use at your own risk!

The project vision is described above. Notably, scan2drive is already feature complete. We don’t want to add any more features to it than it currently has.

scan2drive was published in the hope that it could be useful to others, but the main author has no time to create an active community around it or accept contributions in a timely manner. All support, development and bug fixes are strictly best effort.

Supported scanners

scan2drive can scan from any AirScan-compatible scanner. This means any scanner that is marketed as compatible with Apple iPhones should work. You can find a list of tested devices at https://github.com/stapelberg/airscan#tested-devices
Fujitsu ScanSnap iX500 connected via USB

Architecture

Directory structure

The scans directory (-scans_dir flag) contains the following files:

<sub>/ is the per-user directory under which scans are placed
2016-05-09-21:05:02+0200/ is a directory for an individual scan
- page*.jpg are the raw pages obtained by calling scanimage
- scan.pdf is the converted PDF
- thumb.png is the first page of the converted PDF for display in the UI
- COMPLETE.* are empty files recording which individual processing steps are done

Any file in the scans directory can be deleted at will, with the caveat that deleting scans before the COMPLETE.uploadoriginals file is present will result in that scan being irrevocably lost.

The state directory (-state_dir flag) contains the following files:

cookies.key is a secret key with which cookies are encrypted
sessions/ contains session contents
users/ is a directory containing per-user data
users/<sub>/ is a directory for an individual user
- drive_folder.json contains information about the selected destination Google Drive folder. In case this file is deleted, the user will need to re-select the destination folder and scans cannot be uploaded until a new destination folder has been selected.
- token.json contains the offline OAuth token for accessing Google Drive on behalf of the user. In case this file is deleted, the user will need to re-login. In case this file is leaked, the user should revoke the token

Installation

First, install gokrazy.

Then, pack the github.com/stapelberg/scan2drive/cmd/scan2drive Go package.

As an example, assuming your SD card is accessible as /dev/sdx:

gokr-packer -overwrite=/dev/sdx github.com/stapelberg/scan2drive/cmd/scan2drive

Boot your Raspberry Pi 3 from this SD card and connect the Fujitsu ScanSnap iX500 document scanner via USB (no other scanner is supported).

You should be able to access the gokrazy web interface at the URL which gokr-packer printed. To access the scan2drive web interface, switch to port 7120.

Building with libjpeg-turbo

libjpeg-turbo is a JPEG image codec that uses SIMD instructions (Arm Neon in case of the Raspberry Pi) to accelerate baseline JPEG compression.

scan2drive can optionally make use of libjpeg-turbo (via the turbojpeg build tag), but doesn’t include it by default because of the cumbersome setup.

Using libjpeg-turbo on gokrazy requires a few extra setup steps. Because gokrazy does not include a C runtime environment (neither libc nor a dynamic linker), we need to link scan2drive statically.

Install the gcc cross compiler, for example on Debian:
```
apt install crossbuild-essential-arm64
```
Enable cgo for your gokrazy instance. This means setting the following environment variables when calling gokr-packer:
```
export CC=aarch64-linux-gnu-gcc
export CGO_ENABLED=1
```

Enable static linking and the turbojpeg build tag for scan2drive:

mkdir -p buildflags/github.com/stapelberg/scan2drive/cmd/scan2drive
echo '-ldflags=-linkmode external -extldflags -static' > buildflags/github.com/stapelberg/scan2drive/cmd/scan2drive/buildflags.txt

mkdir -p buildtags/github.com/stapelberg/scan2drive/cmd/scan2drive
echo turbojpeg > buildtags/github.com/stapelberg/scan2drive/cmd/scan2drive/buildtags.txt