Best-Fit Strip Pack

A TypeScript implementation of the online best-fit algorithm for the 2D rectangular strip packing problem. The strip packing problem involves packing rectangles of varying dimensions into a strip of fixed width and infinite height, minimizing the total height used.

The algorithm places each rectangle in the position that minimizes the increase to the overall strip height, processing items sequentially in insertion order without pre-sorting. This makes it suitable for real-time scenarios where rectangles arrive one by one.

Based on the best-fit heuristic described in "The best-fit heuristic for the rectangular strip packing problem: An efficient implementation and the worst-case approximation ratio" by Shinji Imahori and Mutsunori Yagiura.

Features

• Online Best-Fit Heuristic: Places each rectangle in the position that minimizes the increase to overall strip height, processing items in insertion order
• Real-time Processing: Handles rectangles sequentially without pre-sorting or post-processing
• Rotation Support: Optional variant that automatically considers both rectangle orientations for better space utilization
• Optimized Data Structures: Uses linked lists and min-heaps for high-performance operations

Installation

Install via npm

npm install best-fit-strip-pack

Install via yarn

yarn add best-fit-strip-pack

Install via pnpm

pnpm install best-fit-strip-pack

Usage

Basic Packing (Without Rotation)

import { BestFitStripPack } from 'best-fit-strip-pack';

// Create an instance for a strip of width 100 units
const bfsp = new BestFitStripPack(100);

// Insert rectangles
console.log(bfsp.insert(30, 20)); // { x: 0, y: 0 }
console.log(bfsp.insert(20, 40)); // { x: 30, y: 0 }
console.log(bfsp.insert(60, 10)); // { x: 0, y: 40 }

// Get current packed dimensions
console.log(`Used width: ${bfsp.packedWidth}, height: ${bfsp.packedHeight}`);

// Reset for a new packing sequence
bfsp.reset();

Packing with Rotation

import { BestFitStripPackRotatable } from 'best-fit-strip-pack';

const bfsp = new BestFitStripPackRotatable(100);

// The algorithm will automatically choose the best orientation
console.log(bfsp.insert(40, 60));
// { x: 0, y: 0, rotated: true } - rectangle was rotated to 60x40

console.log(bfsp.insert(30, 20));
// { x: 60, y: 0, rotated: false } - placed in original orientation

Batch Processing

import { BestFitStripPack } from 'best-fit-strip-pack';

const rectangles = [
  { width: 30, height: 40 },
  { width: 20, height: 60 },
  { width: 50, height: 30 },
  { width: 10, height: 20 },
  { width: 60, height: 50 },
];

const bfsp = new BestFitStripPack(100);

const packedItems = [];

for (const rect of rectangles) {
  const position = bfsp.insert(rect.width, rect.height);
  packedItems.push({ ...rect, ...position });
}

console.log(`Final strip height: ${bfsp.packedHeight}`);
// Final strip height: 110

console.log('Packed items:', packedItems);
// Packed items: [
//   { width: 30, height: 40, x: 0, y: 0 },
//   { width: 20, height: 60, x: 30, y: 0 },
//   { width: 50, height: 30, x: 50, y: 0 },
//   { width: 10, height: 20, x: 50, y: 30 },
//   { width: 60, height: 50, x: 0, y: 60 }
// ]

API Reference

Core Classes

BestFitStripPack

Main class implementing the Best-Fit algorithm without rotation.

new BestFitStripPack(stripWidth: number)

Properties:

• packedHeight: number - Current total height of the packed strip
• packedWidth: number - Current total width of the packed strip
• stripWidth: number - Fixed width of the strip

Methods:

• insert(width: number, height: number): { x: number; y: number }
• reset(): void

---

BestFitStripPackRotatable

Extends the basic algorithm to support rectangle rotation.

new BestFitStripPackRotatable(stripWidth: number)

Properties:

• packedHeight: number - Current total height of the packed strip
• packedWidth: number - Current total width of the packed strip
• stripWidth: number - Fixed width of the strip (readonly)

Methods:

• insert(width: number, height: number): { x: number; y: number; rotated: boolean }
• reset(): void

Code documentation

The complete API reference of the library is available at the code documentation site.

Issues and Support

If you encounter any issues or have questions, please open an issue.

License

This project is licensed under the MIT License.