SpotiPi

This program uses Spotify API and websockets to control Raspberry Pi and display song album art on LED strip lights.

About SpotiPi

Tech Stack

• Node
• Express.js
• PostgreSQL
• Liquid.js
• socket.io
• Spotify API
• Raspberry Pi

K-Means Clustering Algorithm

A K-Means Clustering algorithm was implemented to determine the k dominant colors for a given image.

Given a collection of points in D-dimensional space (music preferences, birthday, etc.), natural clusters form. Such is the case with dominant colors in an image. Clustering can be applied to a weighted graph G=(V,E) where each cluster has a distance from another cluster $d_{ij}$. To determine a clustering of points that maximizes the distance between clusters such that the distance among points in those clusters are minimized, the following algorithm is used:

1. Convert the image into a 2D array of LAB values.
2. At random, select k points from the 2D array which are the k centroids.
3. For each point p in the array:
   1. Determine the Euclidean distance from p to each centroid.
   2. Add the point p to the centroid cluster with the minimum Euclidean distance.
4. If more than 2 of the resulting clusters have length 0 (i.e. when the album art has very little color variation), restart kmeans to pick new random centroids. Else, replace clusters of length 0 with the cluster of max length to avoid recursing for a long period of time.
5. Determine the mean of each of the k clusters, these are the new centroids.
6. If the new centroids = old centroids, return the resulting cluster. Else, repeat from step 3.

Setup

Spotify API

1. Create an account and login to https://developer.spotify.com/
2. Create the SpotiPi app
3. Note the app Client ID and Client Secret
4. Set the redirect URI to http://[RASPBERRY PI IP]:8888/

PostgreSQL Database

This database stores the results of the kmeans algorithm for a given Spotify albumID to avoid recalculations in the future.

1. Download PostgreSQL from https://www.postgresql.org/download/
2. Open Postgres. There should be 3 default databases, [root name], postgres, and template0. Double click [root name] or run psql -p5432 "[root name]" in the terminal.
3. Create the spotipi database.

CREATE DATABASE spotipi;

4. Exit out of [root name] by running \quit. Open the newly create database by double clicking spotipi in Postgres or running psql -p5432 spotipi in the terminal.
5. Create the table colors.

CREATE TABLE colors (
   albumID VARCHAR(255) UNIQUE,
   colors VARCHAR(255)[]
 );

6. Exit using \quit

Express Server on Raspberry Pi

1. ssh [RASPBERRY PI IP]

2. git clone https://github.com/ajtadeo/Spotipi.git

3. cd Spotipi

4. To use node-canvas and perform server-side image analysis, the following requirements must be met.

   • Node version 16.16.0. Check your node version with node -v.
   • Install the following packages:
     • MacOS:

       brew install pkg-config cairo pango libpng jpeg giflib librsvg 

     • Windows:

       sudo apt-get pkg-config cairo pango libpng jpeg giflib librsvg

   NOTE: If you get the following error gyp: Call to 'node -e "require('nan')"' returned exit status 1 while in binding.gyp. while trying to load binding.gyp, you must install the package nan via npm i nan before installing node-canvas.

5. npm i

6. touch .env

7. Edit .env to include the following variables:

SPOTIFY_CLIENT_ID="s3cret" /* Generated from https://developer.spotify.com/ */
SPOTIFY_CLIENT_SECRET="s3cret" /* Generated from https://developer.spotify.com/ */
SPOTIFY_REDIRECT_URI="http://[HOSTNAME]:[PORT]/auth/callback/"
SESSION_SECRET="s3cret"
PGUSER="root" /* machine's currently logged in user */
PGPASSWORD="root password" /* machine's currently logged in user password */
PGDATABASE="spotipi"
PGHOST="localhost"
PGPORT="5432"

8. Open Postgres.
9. pm2 start app.js

Using the App

1. Open [RASPBERRY PI IP]:8888 in a web browser

Resources

• https://dev.to/bogdaaamn/run-your-nodejs-application-on-a-headless-raspberry-pi-4jnn
• https://sonyarouje.com/2010/12/17/approach-to-count-dominant-colors-in-a-image/
• https://tatasz.github.io/dominant_colors/
• https://dordnung.de/raspberrypi-ledstrip/
• https://towardsdatascience.com/extracting-colours-from-an-image-using-k-means-clustering-9616348712be