Options

const packer = new MaxRectsPacker(maxWidth, maxHeight, padding = 0, options = {});

maxWidth and maxHeight are the bounds a normal bin stays inside. The placeholder bin an oversized rect gets is that rect's own size and can pass them — see oversized rects. padding keeps placed rects at least that many pixels apart, and is added to the footprint of each rect when the packer looks for free space. Omitting it or passing undefined uses 0. Numeric NaN, Infinity and -Infinity throw from the constructor; other JavaScript values retain the existing coercion behaviour, including string concatenation. If that arithmetic produces a non-finite bin size, placement is refused instead of retried indefinitely — see padding troubleshooting. options is a partial IOption:

Option	Default	Effect
smart	true	Grow a bin to the smallest size that still fits, instead of jumping to maxWidth/maxHeight.
pot	true	Round a grown bin up to the next power of two.
square	false	Keep every normal bin square.
allowRotation	false	Allow 90° rotation while packing.
tag	false	Group rects by tag — rect.data.tag, or a tag property on the rect itself.
exclusiveTag	true	With tag, keep one tag per bin and label it with that tag. Set it to false to let several tags share a bin without an automatic bin label.
border	0	Atlas edge spacing: free space is kept border pixels away from a bin's edges.
logic	MAX_EDGE	How free space is scored — see packing logic.

Options are copied by the packer and handed to each bin it creates, so a bin keeps the options it was created with even if you mutate the object you passed in afterwards.

Packing logic

options.logic picks the score findNode() uses to choose among the free rectangles a bin keeps:

Value	Name	Chooses
0	PACKING_LOGIC.MAX_AREA	The free space with the smallest loss of area — good for tight, mixed sizes.
1	PACKING_LOGIC.MAX_EDGE	The free space with the smallest loss of either width or height (the default).
2	PACKING_LOGIC.FILL_WIDTH	Fills the current row width-first before starting the next row.

import { MaxRectsPacker, PACKING_LOGIC } from "maxrects-packer";

const packer = new MaxRectsPacker(1024, 1024, 0, { logic: PACKING_LOGIC.FILL_WIDTH });

FILL_WIDTH reports a usable bin.height only with { pot: false, square: false }, and pairs well with allowRotation: true: the other two settings round the grown bin up, so the height stops tracking what was actually filled.

Sizing

With the defaults (smart: true, pot: true) a bin starts small and grows only as far as the rect being placed requires, then rounds up to a power of two — so a packer declared as 4096 × 4096 that only ever sees 100×100 rects produces a 128×128 bin rather than a 4096×4096 one. square: true additionally takes the larger of the two dimensions, and border is subtracted from the usable area on every side.