liteqr

Fast and Compact QR Code Encoder / Generator.

Why Another Library?

There are already a lot of different QR Code libraries, but this one is specifically optimized for generating QR Codes on web-sites directly in a browser (canvas) with a primary focus on reduced code size (~1.4KB).

Features

• Compact: ~1.4KB minified, zero dependencies.
• Fast: pre-computed presets, cached functional patterns.
• Presets: 40 versions and 4 error correction levels (L, M, Q, H).
• Fully Tested: Identical output to the reference nayuki implementation.

Install

npm install liteqr

Usage

import { qrEncode } from 'liteqr';
import QR_2_L from 'liteqr/presets/2-L';

const text = new TextEncoder().encode('hello');
// Check if the current preset has enough space to store text
if (QR_2_L.s < text.length) {
  throw Error('Not enough space');
}
const matrix = qrEncode(QR_2_L, text);

const size = QR_2_L.gs; // grid size (e.g. 25 for version 2)
const scale = 10; // pixels per module
const quietZone = 4 * scale; // quiet zone (4 modules padding)
const ssize = size * scale; // scaled size

const canvas = document.createElement('canvas');
canvas.width = canvas.height = ssize + quietZone * 2;
const ctx = canvas.getContext('2d');

// Shift origin by quiet zone offset
ctx.translate(quietZone, quietZone);

let p = 0;
for (let y = 0; y < ssize; y += scale) {
  for (let x = 0; x < ssize; x += scale) {
    // Fill only values with the least significant bit 1
    if (matrix[p++] & 1) {
      ctx.fillRect(x, y, scale, scale);
    }
  }
}
document.body.appendChild(canvas);

Presets

Each preset contains pre-computed data for a specific QR Code version and error correction level:

liteqr/presets/{version}-{level}

• version: 1-40
• level: L (Low), M (Medium), Q (Quartile), H (High)

Payload Capacity

Version	L	M	Q	H
1	16	13	10	6
2	31	25	19	13
3	52	41	31	23
4	77	61	45	33
5	105	83	59	43
6	133	105	73	57
7	153	121	85	63
8	191	151	107	83
9	229	179	129	97
10	270	212	150	118
11	320	250	176	136
12	366	286	202	154
13	424	330	240	176
14	457	361	257	193
15	519	411	291	219
16	585	449	321	249
17	643	503	363	279
18	717	559	393	309
19	791	623	441	337
20	857	665	481	381
21	928	710	508	402
22	1002	778	564	438
23	1090	856	610	460
24	1170	910	660	510
25	1272	996	714	534
26	1366	1058	750	592
27	1464	1124	804	624
28	1527	1189	867	657
29	1627	1263	907	697
30	1731	1369	981	741
31	1839	1451	1029	789
32	1951	1537	1111	841
33	2067	1627	1167	897
34	2187	1721	1227	957
35	2302	1808	1282	982
36	2430	1910	1350	1050
37	2562	1988	1422	1092
38	2698	2098	1498	1138
39	2808	2212	1578	1218
40	2952	2330	1662	1272

Grid Size

Version	Size
1	21
2	25
3	29
4	33
5	37
6	41
7	45
8	49
9	53
10	57
11	61
12	65
13	69
14	73
15	77
16	81
17	85
18	89
19	93
20	97
21	101
22	105
23	109
24	113
25	117
26	121
27	125
28	129
29	133
30	137
31	141
32	145
33	149
34	153
35	157
36	161
37	165
38	169
39	173
40	177

Design Trade-offs

ECI/UTF-8 Only

liteqr encodes all payloads as ECI (designator 26 = UTF-8) byte-mode segments. This makes the payload bit-stream byte-aligned and simplifies the encoder. For most real-world use cases (international text, URLs with mixed characters) this is a net win.

Pre-computed Presets

Each version + error-correction-level combination is shipped as a separate preset module (liteqr/presets/{version}-{level}). A preset contains grid size, payload size, generator polynomial, headers, alignment pattern positions, etc. The downside is that you must manually select a version with enough capacity for your payload — the library won't automatically choose the smallest version that fits. The upside is that since you explicitly control which version is used, you know the exact grid size and pixel dimensions upfront, which allows you to render onto a canvas without any aliasing or rounding artifacts.

Mask Pattern 0

Only mask pattern 0 ((x + y) % 2 === 0) is supported. The QR specification defines 8 patterns and recommends selecting the one that minimizes errors. Since this library is optimized for web-site rendering, QR codes will be displayed on good screens with clean rendering, making the difference between mask patterns negligible in practice.

License

MIT OR Apache-2.0