qrcode-rs 1.5.0

#![cfg(feature = "decode-rqrr")]
//! [`rqrr`](https://crates.io/crates/rqrr)-backed [`QrDecoder`] adapter.
//!
//! Enables decoding a rendered QR image back to its payload via the `rqrr`
//! crate. rqrr performs its own adaptive thresholding, so a plain grayscale
//! [`GrayPixels`] view is all that is required.

use crate::decode::{DecodedQrCode, GrayPixels, QrDecoder};
use crate::types::{EcLevel, Version};

/// A [`QrDecoder`] backed by the [`rqrr`] crate.
#[derive(Default, Debug, Clone, Copy)]
pub struct RqrrDecoder;

impl RqrrDecoder {
    /// Creates a new `RqrrDecoder`.
    #[must_use]
    pub fn new() -> Self {
        Self
    }
}

impl QrDecoder for RqrrDecoder {
    type Error = rqrr::DeQRError;

    fn decode(&self, image: GrayPixels<'_>) -> Result<Vec<DecodedQrCode>, Self::Error> {
        let mut prep =
            rqrr::PreparedImage::prepare_from_greyscale(image.width() as usize, image.height() as usize, |x, y| {
                image.get(x as u32, y as u32)
            });
        let grids = prep.detect_grids();
        let mut out = Vec::new();
        for grid in grids {
            let mut bytes: Vec<u8> = Vec::new();
            let meta = grid.decode_to(&mut bytes)?;
            out.push(DecodedQrCode::new(bytes, map_version(meta.version), map_ec(meta.ecc_level)));
        }
        Ok(out)
    }
}

/// Maps an `rqrr` version to a crate [`Version`] (rqrr decodes only normal QR,
/// so the value is always in `1..=40`).
fn map_version(v: rqrr::Version) -> Version {
    Version::Normal(v.0 as i16)
}

/// Maps an `rqrr` ecc level (`u16` 0..=3) to a crate [`EcLevel`].
fn map_ec(level: u16) -> EcLevel {
    match level {
        0 => EcLevel::L,
        1 => EcLevel::M,
        2 => EcLevel::Q,
        _ => EcLevel::H,
    }
}