Photo Mosaic App

A pure JavaScript client-side app that loads an image and generates a photo-mosaic of the original image, making effective use of parallel and asynchronous functions through HTML5 features like Web Workers and Promises.

Goal

The goal of this task is to implement the following flow in a client-side app.

1. A user selects a local image file.

2. The app loads that image, divides the image into tiles, computes the average color of each tile, fetches a tile from the server for that color, and composites the results into a photomosaic of the original image.

3. The composited photomosaic should be displayed according to the following constraints:

   • the mosaic should be rendered from the top row to the bottom row.

4. The client app should make effective use of parallelism and asynchrony.

Guidelines

The project skeleton contains a lightweight server (written in node) for serving the client app and the tile images. To start it, run npm start.

/ serves mosaic.html

/js/* serves static resources

/color/ serves an SVG mosaic tile for color . e.g., /color/0e4daa

The tile size should be configurable via the code constants in js/mosaic.js. The default size is 16x16.

Requirements:

• Make the code modular;
• Make the code testable;
• Not use JS libraries (e.g., jQuery, Modernizr, React) as browser APIs are sufficient for the project;
• Use HTML5 features where appropriate;

Solution

It was created and exposed a module called PhotoMosaic to manage everything related to the generation of the photo mosaic. To get a better performance and optimization, it was used Promise and Worker (HTML5 features) to process the operations asynchronously, with the former, and the havy ones in parallel, with the latter.

The PhotoMosaic module, through the generate function, returns a promise so when every tile is processed and loaded it responds with a canvas with the photomosaic image ready to be displayed.

Running the application

Download the project

Download or clone the project using following command:

$ git clone https://github.com/gustavomazzoni/photo-mosaic

Run locally

Start the server

$ npm start

Then, open on your browser: http://localhost:8765/

Demo

This demo has a bad performance due to heroku limitation on concurrent web requests, since I'm using its standard free container. So it takes to long to download the SVG mosaic tiles. http://photomosaic-mazzoni.herokuapp.com/