Multi Bin Packer

This is a 2d bin packer for the special purpose of creating spritesheets for CSS and games.

It differs from the long list of similar packages by its packing approach: Instead of creating one output bin with a minimum size this package is trying to create a minimum number of bins under a certain size. This avoids problems with single massive image files that are not browser-friendly. This can be especially useful for WebGL games where the GPU will benefit from spritesheets close to power-of-2 sizes.

Usage:

npm install multi-bin-packer --save

let MultiBinPacker = require("multi-bin-packer");
let packer = new MultiBinPacker(1024, 1024);
 
packer.addArray([
    {width: 600, height: 20, data: {name: "tree", foo: "bar"}},
    {width: 600, height: 20, data: {name: "flower"}},
    {width: 2000, height: 2000, data: {name: "oversized background"}},
    {width: 1000, height: 1000, data: {name: "background"}},
    {width: 1000, height: 1000, data: {name: "overlay"}}
]);
 
console.log(packer.bins.length); // 3
console.log(packer.bins[0].width, packer.bins[0].height); // 2000 2000
console.log("%j", packer.bins[0].rects); // [{"x":0,"y":0,"width":2000,"height":2000,"data":{"name":"oversized background"},"oversized":true}]
console.log(packer.bins[1].width, packer.bins[1].height); // 1000 1020
console.log("%j", packer.bins[1].rects); // [{"width":1000,"height":1000,"x":0,"y":0,"data":{"name":"background"}},{"width":600,"height":20,"x":0,"y":1000,"data":{"name":"tree","foo":"bar"}}]
console.log(packer.bins[2].width, packer.bins[2].height); // 1000 1020
console.log("%j", packer.bins[2].rects); // [{"width":1000,"height":1000,"x":0,"y":0,"data":{"name":"overlay"}},{"width":600,"height":20,"x":0,"y":1000,"data":{"name":"flower"}}]

API

Note: multi-bin-packer requires node >= 4.0.0

new MultiBinPacker(maxWidth, maxHeight[, padding])

Creates a new Packer. maxWidth and maxHeight are passed on to all bins. If padding is supplied all rects will be kept at least padding pixels apart.

packer.add(width, height, data)

Adds a rect to an existing bin or creates a new one to accomodate it. data can be anything, it will be stored along with the position data of each rect.

packer.addArray([{width: width, height: height, data: data}, ...])

Adds multiple rects. Since the input is automatically sorted before adding this approach usually leads to fewer bins created than separate calls to .add()

packer.bins

Array of bins. Every bin has a width and height parameter as well as an array rects.

packer.bins[n].rects

Array of rects for a specific bin. Every rect has x, y, width, height and data. In case of an rect exceeding maxWidth/maxHeight there will also be an oversized flag set to true.

Support for oversized rectangles

Nornally all bins are of equal size or smaller than maxWidth/maxHeight. If a rect is added that individually does not fit into those constraints a special bin will be created. This bin will only contain a single rect with a special "oversized" flag. This can be handled further on in the chain by displaying an error/warning or by simply ignoring it.

Packing algorithm

Currently a simple binary tree bin packer algorithm is used. More efficient packing algorithms might be implemented in the future. PRs are welcome.

If addArray() is used rects are sorted before being packed, leading to improved packing efficiency.