qrkit/decode

Decode a QR module matrix back into text.

from_rows reads a Standard QR, Micro QR or rMQR symbol given as rows of modules (True is dark), the shape qrkit.rows returns. A light quiet zone around the symbol is removed first, and the symbol may be rotated or mirrored. Damaged codewords are repaired with Reed-Solomon error correction up to the level’s capacity.

This reads a grid of modules, not a photo: locating a symbol in a camera image, perspective correction and thresholding are out of scope.

import qrkit
import qrkit/decode

pub fn round_trip() -> Result(String, Nil) {
  let assert Ok(qr) = qrkit.encode("https://example.com")
  case decode.from_rows(qrkit.rows(qr)) {
    Ok(decoded) -> Ok(decode.text(decoded))
    Error(_) -> Error(Nil)
  }
}

pub opaque type Decoded

pub type StructuredAppend {
  StructuredAppend(position: Int, total: Int, parity: Int)
}

pub fn eci(decoded: Decoded) -> option.Option(Int)

pub fn error_correction(
  decoded: Decoded,
) -> types.ErrorCorrection

pub fn errors_corrected(decoded: Decoded) -> Int

pub fn from_rows(
  rows: List(List(Bool)),
) -> Result(Decoded, error.DecodeError)

pub fn mask(decoded: Decoded) -> Int

pub fn structured_append(
  decoded: Decoded,
) -> option.Option(StructuredAppend)

pub fn symbol(decoded: Decoded) -> types.Symbol

pub fn text(decoded: Decoded) -> String

pub fn version(decoded: Decoded) -> Int