finscn / maxrects-packer

A max rectangle 2d bin packer npm-module for packing glyphs or images into multiple sprite-sheet/atlas

Max Rects Packer

A simple max rectangle 2d bin packing algorithm for packing glyphs or images into multiple sprite-sheet/atlas. Minimalist with no module dependency.

This is a evolved version of Multi-Bin-Packer with much effiecent packing algorithm. All interfaces and methods are inherited so no tweaks needed in your current code except module name.

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.

And you can also save/load to reuse packer to add new sprites. (Below is a demo atlas packed with two difference bitmap fonts)

Usage:

Notice: Since version 2.0.0beta Max Rects Packer is rewritten in typescript and change the import method from old require("maxrects-packer") to require("maxrects-packer").MaxRectsPacker or more fashioned import statement.

npm install maxrects-packer --save

let MaxRectsPacker = require("maxrects-packer").MaxRectsPacker;
const options = {
    smart: true,
    pot: true,
    square: false
}; // Set packing options
let packer = new MaxRectsPacker(1024, 1024, 2, options); // width, height, padding, options

let input = [
    {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"}}
];

packer.addArray(input); // Start packing with input array
packer.bins.forEach(bin => {
    console.log(bin.rects);
});

// Reuse packer 
let bins = packer.save();
packer.load(bins);
packer.addArray(input);

Test

npm test

API

Note: maxrects-packer requires node >= 4.0.0

new MaxRectsPacker(maxWidth, maxHeight[, padding, options])

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.

• options.smart packing with smallest possible size. (default is true)
• options.pot bin size round up to smallest power of 2. (defalt is true)
• options.square bin size shall alway be square. (defaut is false)

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()

let bins = packer.save()

Save current bins settings and free area to an Array of objects for later use. Better to JSON.stringify(bins) and store in file.

packer.load(bins)

Restore previous saved let bins = JSON.parse(fs.readFileSync(savedFile, 'utf8')); settings and overwrite current one. Continue packing and previous packed area will not be overlaped.

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

Use Max Rectangle Algorithm for packing, same as famous Texture Packer