Snack Watcher Web Application
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Snack Watcher

Starting as a fun Jonah Group project, the Snack Watcher is designed to watch the company's "Snack Table". If there are some new "Snacks" presented on the "Snack Table", it can be used to report the event onto chat channels, emails or messages saying "Snack Happened!", posting an image and trying to classify the snacks that it observed. It supports both as web site for interactive snack viewing and RESTful API for programmatic snack querying.

It is open source in hope of advancing the sharing spirit and snacking fun within your company!

Snack Watcher Blog

Snack Watcher Team has a blog site hosted at

Snack Watcher Logo Snack Watcher Blog

posting the latest development articles, interesting researches and on-going discussions on the Snack Watcher project.

Snack Classifier (optional RESTful API)

Snack Classifier, which is an independent image classification Microservice, it can extend the functionality of Snack Watcher.

Snack Watcher Web

Before diving into the technical details, a brief overview of how Snack Watcher could benefit the use case of watching a "Snack Table". Also, much effort has been devoted to make it working well with a Raspberry Pi 2 or 3, such that the cost of setup will be minimal and elegant in the geekiest way. The term snack-web as a synonym as "Snack Watcher Web" in here.

  • Raspberry Pi setup on the "Snack Table"

Snack Watcher Setup 1

  • Webcam connected to watch at the "Snack Table"

Snack Watcher Setup 2

  • snack-web captured image sample with blob status (green means New, red means removed) and blob classification (they looks like "package" from classifier training)

Snack Web Image Capture


snack-web is a web application showing the result of snack watching, which has been designed to configure and run with Raspberry Pi 2 or 3. snack-web could be driven, either manually (via Web) or programmatically (via RESTful API) to take pictures and push the snapshots into the static/images directory. The RESTful API approach to programmatically watch and return the images should be the key feature to integrate with a system, providing greater utilities to report the snack status.

Note: snack-web will be served from http://localhost:8000 by default. If this is not the case, replace the hostname with the actual configured site location.

snack-web Front Page

The following illustrated the front page of snack-web, the front page menu items are listed:

  • Links: display the last N snack captured image and it's processing stages
  • Calibrate: take a background image for calibrating the background colour
  • Snap: snap a snack image from the camera now
  • Teach: (Require advanced setup) Currently still under heavy development, the teaching module is designed to interactively classify snack for future training. This required classifier setup to work.

Snack Web Front Page

For each snack image capture, it collects the set of processing stage images for debugging and understanding how the snacks are identified. For each blob that the system detected, it will be stored for displaying and training. The colour coded blobs represent, green is the new detected blob, yellow is the stationary blob, and red is the removed blob. By click on each image bar, a larger image will be shown for detail inspections.

Snack Web Item Display

Install OpenCV and SimpleCV

snack-web is built on the popular OpenCV and SimpleCV. OpenCV is a C++ library of programming functions mainly aimed at real-time computer vision. SimpleCV provides the Python wrapper on top of OpenCV, simplified many image processing, classifying and displaying functions.

Learning from this Install Notes, it describes a super easy and fast way to setup your Raspberry Pi with OpenCV with SimpleCV module, avoiding many painful steps described by others blogs

Simply run the following shell commands to install the OpenCV and it's necessary dependencies:

sudo apt-get update
sudo apt-get upgrade

sudo apt-get install python-setuptools
sudo apt-get install python-pip
sudo apt-get install ipython python-opencv python-scipy python-numpy python-pygame

After all OpenCV and dependencies are installed, we could proceed to install SimpleCV, a wrapper API that make computer vision really easy. It could be download from github and install from the source.

sudo pip install
sudo pip install svgwrite

Setup Requirements

Install Python Requirements

Assumed that OpenCV and SimpleCV are installed, snack-web Python requirements can be installed by,

sudo pip install -r requirements.txt

Install MongoDB

snack-web is using mongodb as the storage for image attributes. The instructions of installing Raspberry Pi mongodb binaries should be followed closely, which has been confirmed to work Raspberry Pi 2 & 3.

As a quick mongodb service guide,

  • starting up the mongodb service by
sudo service mongodb start
  • checking the status by
sudo service mongodb status
  • shutting down cleanly by
sudo service mongodb stop

Configure System

The default configuration of the system located in configuration/environment.ini (refer to the Configuration Keys table for their usage)

How to Run

Step 1: Quick Start to Verify

Keys: Debug is True, Use Web Camera is False

The system is set to DEBUG=True after the first checkout. When DEBUG is true, instead of using a camera to capture images, the system will be a set of simulated cookie images to demonstrate the system behaviour. At this stage, you simply want to verify the system has been installed and configured properly with MongoDB. The default MongoDB is configured by DB_CONNECT_STRING to run on localhost.

Run System

Once the requirements are installed, mongodb has started and the system has been configured, snack-web app is started with:

python runserver

Navigate to http://localhost:8000 to see the snack-web front page.

Snack Web Startup

Click Calibrate to perform initialization

Snack Web Startup

Click Snap to capture an image (simulated image capture since DEBUG=True)

Snack Web Startup

Click Links to see the captured image list

Snack Web Startup

Step 2: Turn On Camera and Action

Keys: Debug is False, Use Web Camera is True

After verifying the system has been installed and connected successfully with Step 1, the camera could be switch ON by USE_WEB_CAMERA=True. You can use the Snap menu function to force capture an image. You should see the latest captured image has been processed and shown on the Links menu. Congratulation! the snack watcher web application is configured and operational.

Run System

Once the USB camera has been plugged-in, snack-web app is started with:

python runserver

Navigate to http://localhost:8000 to see the snack-web front page.

  • Click Calibrate to perform initialization
  • Click Snap to capture a Camera image
  • Click Links to see the captured image list

Step 3: More Configuration (Optional)

The system is operational after the previous 2 steps. If you like to continue tuning the system behaviours. The following configuration keys are available:

Table: snack-web Configuration Keys

Section Key Default Description
system HOST snack-web is serving from this IP address
system PORT 8000 snack-web is running from this port
system DEBUG True switch debugging mode
system HAS_FTP False switch ftp transfer mode
system PRE_INIT_CAMERA False switch if system should pre-initial the camera
system USE_WEB_CAMERA False switch if using USB web camera
system USE_MOTION_CAMERA False switch if using motion snapshot as the capture image
system MOTION_CAMERA_SNAPSHOT lastsnap.jpg location to find motion snapshot image
system CROP_IMAGE_BORDER (25,25) crop the captured image border by (X,Y) amount. The top left corner from (0,0) to (X,Y) will be used by auto background calibration if BACKGROUND_AUTO_CALIBRATE is True.
system SHOW_REMOVED_SNACKS True render the removed (disappeared) snacks with red boxes
system USE_COLOR_DISTANCE_FOR_BACKGROUND True calculate the background difference by color (R,G,B) distance metrics
system BACKGROUND_MASK_THRESHOLD 100 distance from the calibrated background color which the pixels are thresholded as background.
system BACKGROUND_AUTO_CALIBRATE True switch if using the top left corner defined by CROP_IMAGE_BORDER as background calibration sample.
database DB_CONNECT_STRING {mongodb URL} connect to the specified mongodb URL
database DB {mongodb name} connect to the specified mongodb name
classifier USE_CLASSIFIER False (Advanced) switch to use api-classifier RESTful service to classify a blob from the captured image
classifier CLASSIFIER_URL {api-classifier URL} (Advanced) connect to the specified api-classifier URL for classifying services
ftp FTP_HOST {ftp host} connect to the specified host for image upload
ftp FTP_PORT {ftp port} port for remote ftp connection
ftp HTTP_PORT {http port} port for remote http connection
ftp FTP_USER {ftp username} ftp username for login if needed
ftp FTP_PASS {ftp password} ftp password for login if needed


http://snack-web:8000/api (Replace snack-web with your host location.)

The images and operations can also be accessed via RESTful API. The available URI resources are listed in this table.

Table: snack-web RESTful API

API HTTP Description
/snacks/ GET return all images, that could be a lot of images
/snacks/snap GET take a snapshot and return the latest image. This call takes a snapshot and returns the processed image.
/snacks/id/{id} GET return image {id}. This call gets an image by the database id. If it is not found, null is returned.
/snacks/state/{class_state} GET Get all blobs matched the given class_state. This call gets a list of blobs filtered by c1ass_state.
/snacks/state PUT Update blobs state info by _id. This call accepts a list of (id, c1ass, c1ass_state) objects, updates their associated blobs in the database.
/snacks/class/names GET Get the list of class names. This call returns a list of the class names that a blob can be classified by.
/snacks/last GET Get the last image. This call returns the latest image by date_created DESC. If none exist, null is returned.
/snacks/last/{int:n} GET Get the last n images. This call returns a list of the latest n images by date_created DESC.
/snacks/last/summary GET Get the latest summary. This call returns a summary of the latest processed images including the new, duplicate and removed blobs. If no images exist, it returns null.

Snapshot Naming Convention

When a camera snapshot is taken, The images will be written into a creation folder according to the snapshot's date-time,


e.g. snack-2015_06_17-13_14_58 is created at date 2015-06-17 and time 13:14:58.

The result JSON for an image, for example, requests for the last image using curl command.

curl http://snack-web:8000/api/snacks/last

For a list of images, for example, requests for all snack images using curl command.

curl http://snack-web:8000/api/snacks/

Supervisor for Execution Monitoring

Supervisor daemon is a host process, monitoring a running process and starting the monitored process if necessary. On the remote host, the supervisor configuration should be installed under /etc/supervisor/conf.d directory.

We have prepared deployment/supervisor/snack-web.conf for supervisor, just need to copy to the configuration directory.

sudo cp snack-web.conf /etc/supervisor/conf.d/.

After the snack-web.conf has been installed, we can start the supervisor daemon to monitor the snack-web process.

sudo supervisord -c /etc/supervisor/supervisord.conf

We can further control the supervisor daemon, to see it's status, to start and to stop monitored processes.

sudo supervisorctl status
sudo supervisorctl start
sudo supervisorctl stop