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qrcode

stable

Generates QR codes from text, producing SVG strings, ASCII art, raw module data, or metadata about the encoded content.

use plugin qrcode::{generate, generate_svg, generate_svg_sized, …}
7 functions Image
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Functions (7)
  1. generate Generate QR code as raw module data
  2. generate_svg Generate QR code as an SVG string
  3. generate_svg_sized Generate SVG at a specific pixel size
  4. to_string Render QR code as Unicode block art
  5. generate_with_ec Generate with explicit error correction level
  6. encode_info Get QR metadata without full module data
  7. version_for_length Find minimum QR version for a text length

Overview

qrcode turns any text into a QR code without external tooling. It is stateless and handle-free: every function takes a plain string and returns a ready-to-use value, so there is no encoder object to construct or dispose. You choose the output that fits the destination — a self-contained SVG document for the web, Unicode block art for the terminal, a flat boolean module grid for custom rendering, or a small metadata table when you only need facts about the code.

The core concept is the module grid: a square of size × size cells where each cell is either dark (true) or light (false), stored row-major in a flat table. SVG and ASCII renderers walk that same grid for you, while generate and generate_with_ec hand it back so you can draw it yourself. Error correction level ("L", "M", "Q", "H") trades capacity for resilience; "M" is the default everywhere it is optional.

Common patterns

Render a scannable QR code straight to the terminal:

zolo▶ Playground
use plugin qrcode::{to_string}

print(to_string("https://zolo-lang.dev"))

Produce a fixed-size SVG and report what the encoder picked for it:

zolo▶ Playground
use plugin qrcode::{generate_svg_sized, encode_info}

let url = "https://zolo-lang.dev/docs"
let svg = generate_svg_sized(url, 256)
let info = encode_info(url)
print("version {info["version"]}, {info["size"]}x{info["size"]} modules")
print(svg)

Plan capacity, then draw the raw grid by hand:

zolo▶ Playground
use plugin qrcode::{version_for_length, generate}

let payload = "ORDER-2026-000457"
print("fits in version {version_for_length(payload.len())}")

let qr = generate(payload)
let n = qr["size"]
for y in 0..n {
  let line = ""
  for x in 0..n {
    line = line + (qr["modules"][y * n + x] ? "##" : "  ")
  }
  print(line)
}

generate(text) → table

Generate QR code as raw module data

Encodes the text and returns #{size: int, modules: table}. modules is a flat boolean table (row-major) where true means a dark module. size is the width/height in modules.

zolo▶ Playground
use plugin qrcode::{generate}

let qr = generate("https://zolo-lang.dev")
print("QR size: {qr["size"]}x{qr["size"]}")

Walk the flat module table to count dark cells:

zolo▶ Playground
use plugin qrcode::{generate}

let qr = generate("PING")
let n = qr["size"]
let dark = 0
for i in 0..(n * n) {
  if qr["modules"][i] {
    dark = dark + 1
  }
}
print("{dark} dark modules of {n * n}")

generate_svg(text) → string

Generate QR code as an SVG string

Generates a complete SVG document for the QR code. Includes a 4-module quiet zone margin. Each dark module is a 1-unit <rect>.

zolo▶ Playground
use plugin qrcode::{generate_svg}

let svg = generate_svg("Hello, World!")
// write svg to a file or embed in HTML
print(svg)

generate_svg_sized(text, px_size) → string

Generate SVG at a specific pixel size

Like generate_svg but scales the output to exactly px_size pixels square. Useful when you need a specific canvas dimension.

zolo▶ Playground
use plugin qrcode::{generate_svg_sized}

let svg = generate_svg_sized("https://example.com", 256)
print(svg)

to_string(text, ec_level?) → string

Render QR code as Unicode block art

Renders the QR code as Unicode block characters using half-block glyphs, producing a compact terminal-friendly representation. ec_level is optional: "L", "M" (default), "Q", or "H".

zolo▶ Playground
use plugin qrcode::{to_string}

print(to_string("scan me"))
print(to_string("high reliability", "H"))

Because two module rows are packed into each text line with half-block glyphs, the printout is roughly half as tall as the module grid — handy for logging a code that still scans from the screen:

zolo▶ Playground
use plugin qrcode::{to_string}

let art = to_string("wifi:guest")
print(art)

generate_with_ec(text, ec_level) → table

Generate with explicit error correction level

Like generate but lets you choose the error correction level. Returns #{size, modules, version, ec_level}. EC levels: "L" (7%), "M" (15%), "Q" (25%), "H" (30%).

zolo▶ Playground
use plugin qrcode::{generate_with_ec}

let qr = generate_with_ec("product:12345", "Q")
print("version {qr["version"]}, size {qr["size"]}")

Higher correction levels resist damage but grow the code; compare the size that the same payload needs at the two extremes:

zolo▶ Playground
use plugin qrcode::{generate_with_ec}

let low = generate_with_ec("label", "L")
let high = generate_with_ec("label", "H")
print("L -> {low["size"]} modules, H -> {high["size"]} modules")

encode_info(text) → table

Get QR metadata without full module data

Returns metadata about the QR code without generating full module data. Faster when you only need #{version, size, ec_level, data_bytes}.

zolo▶ Playground
use plugin qrcode::{encode_info}

let info = encode_info("https://zolo-lang.dev/docs")
print("QR version {info["version"]}, {info["data_bytes"]} data bytes")

version_for_length(len) → int

Find minimum QR version for a text length

Returns the minimum QR version (1–40) capable of encoding len alphanumeric characters at error correction level M. Useful for capacity planning.

zolo▶ Playground
use plugin qrcode::{version_for_length}

let url = "https://example.com/very/long/path"
let v = version_for_length(url.len())
print("need at least QR version {v}")
View source code
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