The following is required for running this photobooth application. I used only versions available in the package repositories of Raspbian (tested version numbers are given in brackets), others might work just as well.

Python (2.7.3)
Pygame (1.9.1)
Pillow (2.8.1)
gPhoto (2.5.6)
Optional: RPi.GPIO (0.5.11)

RPi.GPIO is necessary to use external buttons as a trigger but it works just fine without. Triggering is then only possible using touch screen / mouse or key 'c'.

Hardware

Raspberry Pi (Any device able to run the software stack should work fine)
Camera supported by gPhoto. I've used a Canon EOS 500D.
Optional: External button that closes GPIO23 (pin 16) and GND.

Usage

Simply download photobooth.py or clone the repository and run it. It opens the GUI, prints the features of the connected camera, e.g.,

$ ./photobooth.py 
Abilities for camera             : Canon EOS 500D
Serial port support              : no
USB support                      : yes
Capture choices                  :
                                 : Image
                                 : Preview
Configuration support            : yes
Delete selected files on camera  : yes
Delete all files on camera       : no
File preview (thumbnail) support : yes
File upload support              : yes

and waits for you to hit the button to take pictures.

Available actions:

Press q: Exit the application
Press c: Take four pictures, arrange them in a grid and display them for some seconds.
Hit a switch that closes GPIO23 (Pin 16) and GND: Take four pictures, arrange them in a grid and display them for some seconds.
Click anywhere on the screen: Take four pictures, arrange them in a grid and display them for some seconds.

All pictures taken are stored in a subfolder of the current working directory, named YYYY-mm-dd after the current date. Existing files are not overwritten.

Installation

A brief description on how to set-up a Raspberry Pi to use this photobooth software.

Download latest Raspbian image and set-up an SD-card. You can follow these instruction.

If your display needs some additional configuration, change the file config.txt in the boot-partition to your needs. For example, I'm using a Pollin LS-7T touchscreen, for which I need to enter the following to avoid overscan:
```
hdmi_group=2
hdmi_mode=87
hdmi_cvt=1024 600 60 6 0 0 0
```
Insert the SD-card into your Raspberry Pi and fire it up. Use the rpi-config tool that is shown automatically on the first boot to configure your system (e.g., expand partition, change hostname, password, enable SSH, configure to boot into GUI, etc.).
Reboot and open a terminal. Type sudo rpi-update to install the latest software versions. Reboot.
Run sudo apt-get update and sudo apt-get upgrade to upgrade all installed software.
Install any additionally required software:

Pillow:

sudo apt-get install python-dev python-pip libjpeg8 python-tk
sudo pip install Pillow

gPhoto2: sudo apt-get install gphoto2 To ensure the camera can be controlled properly via USB, remove some files:

sudo rm /usr/share/dbus-1/services/org.gtk.Private.GPhoto2VolumeMonitor.service
sudo rm /usr/share/gvfs/mounts/gphoto2.mount
sudo rm /usr/share/gvfs/remote-volume-monitors/gphoto2.monitor
sudo rm /usr/lib/gvfs/gvfs-gphoto2-volume-monitor

xinput_calibrator to calibrate touchscreens:
```
wget http://adafruit-download.s3.amazonaws.com/xinput-calibrator_0.7.5-1_armhf.deb
sudo dpkg -i -B xinput-calibrator_0.7.5-1_armhf.deb
```
Calibrate by calling xinput_calibrator and pasting the showed snippet to a new file /etc/X11/xorg.conf.d/99-calibration.conf (Create the directory if necessary).

Checkout the Photobooth repository

git clone https://github.com/reuterbal/photobooth

Modifications

In the beginning of photobooth.py a number of config options are available. Change them to your liking.

The GUI-class is separated from the entire functionality. I'm using Pygame because it's so simple to use. Feel free to replace it by your favorite library.

License

I provide this code under AGPL v3. See LICENSE.