spriter

NOTE: This is a work in progress

A really simple library for sprite generation.

Includes

• Express middleware
• NodeJS API

Usage

We create a definition of images we would like to serve, where the width/height is the output width/height of the image. Our library will scale the images during packing.

const images = [
  {
    id: "red",
    url: "http://example.com/images/red.png",
    width: 20,
    height: 20
  },
  {
    id: "blue",
    url: "http://example.com/images/blue.jpg",
    width: 20,
    height: 20
  },
];

With the above definition we can either create server with the express middleware.

const spriter = require("spriter");

const fakeDatabase = {
  "acme": images,
};

function fakeApi (req) {
  const {namespace} = req.params;
  return fakeDatabase[namespace];
}

app.use('/:namespace/sprite*', spriter.middleware(fakeApi, {
  // Default values...
  concurrency: 10,
  missingImageRetryInterval: 60,
}));

Or just run the process via the API Via the API

const {buffer, json} = spriter.convert(images);

Which is the same as

const result = spriter.json(images);
const json = result.boxes;
const buffer = await spriter.png(result);

A full example using expressjs can be found at ./example/.

CLI

You can also run a CLI with

spriter --port 8080 --api "http://localhost:3006/{namespace}/images"
spriter --db ./bin/sample/db.js --static ./example/public/images/

Which will expose the following URLS

http://localhost:8080/{namespace}/sprite@{pixel_ratio}x.png
http://localhost:8080/{namespace}/sprite@{pixel_ratio}x.json

So if you clone this repo and run

./bin/cli.js --db ./bin/sample/db.js --static ./example/public/images/

You can access the following URLs

• http://localhost:8080/acme/sprite@1x.png
• http://localhost:8080/acme/sprite@1x.json
• http://localhost:8080/acme/sprite@2x.png
• http://localhost:8080/acme/sprite@2x.json
• http://localhost:8080/facefriend/sprite@2x.json
• http://localhost:8080/facefriend/sprite@2x.json

As defined by ./bin/sample/db.js.

Development

Clone the repo and run

npm install

Start the example server with

npm run example

Where you have access to the following URLs

• http://localhost:3003/ - mapbox-gl-js example map
• http://localhost:3003/acme/sprite@2x.json - the sprite JSON
• http://localhost:3003/acme/sprite@2x.png - the sprite PNG

Note @2x can be replaced with any pixel ratio, for example @1x/@3x.

Test

To test run

npm test

You can view code coverage results in your working directory at ./coverage/index.html

Memory optimization

This library uses sharp under the hood. Using the standard memory allocator on a number of systems appears to use lots of memory, and sometimes doesn't release it. As described in lovell/sharp#955, this can be resolved by using the jemalloc memory allocator, as described in that issue.

If you're on a Debian based system

apt-get update
apt-get install libjemalloc1

Then run the node process using the jemalloc memory allocator.

LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1 npm run example

If you are still seeing issues you can also disable the sharp cache globally (see https://sharp.pixelplumbing.com/api-utility#cache). If you can using the spriter CLI you can disable that with --no-cache option, for example

spriter --no-cache --db ./bin/sample/db.js --static ./example/public/images/

License

MIT