kmx git

use crate::TOTP;
use image::Luma;

pub(crate) fn get_qr_draw_canvas(qr: qrcodegen::QrCode) -> image::ImageBuffer<Luma<u8>, Vec<u8>> {
    let size = qr.size() as u32;
    // "+ 8 * 8" is here to add padding (the white border around the QRCode)
    // As some QRCode readers don't work without padding
    let image_size = size * 8 + 8 * 8;
    let mut canvas = image::GrayImage::new(image_size, image_size);

    // Draw the border
    for x in 0..image_size {
        for y in 0..image_size {
            if (y < 8 * 4 || y >= image_size - 8 * 4) || (x < 8 * 4 || x >= image_size - 8 * 4) {
                canvas.put_pixel(x, y, Luma([255]));
            }
        }
    }

    // The QR inside the white border
    for x_qr in 0..size {
        for y_qr in 0..size {
            // The canvas is a grayscale image without alpha. Hence it's only one 8-bits byte longs
            // This clever trick to one-line the value was achieved with advanced mathematics
            // And deep understanding of Boolean algebra.
            let val = !qr.get_module(x_qr as i32, y_qr as i32) as u8 * 255;

            // Multiply coordinates by width of pixels
            // And take into account the 8*4 padding on top and left side
            let x_start = x_qr * 8 + 8 * 4;
            let y_start = y_qr * 8 + 8 * 4;

            // Draw a 8-pixels-wide square
            for x_img in x_start..x_start + 8 {
                for y_img in y_start..y_start + 8 {
                    canvas.put_pixel(x_img, y_img, Luma([val]));
                }
            }
        }
    }
    canvas
}

/// Convert text to a PNG QR code.
pub fn qr_png(text: &str) -> Result<Vec<u8>, String> {
    use image::ImageEncoder;

    let mut vec = Vec::new();

    let qr: Result<qrcodegen::QrCode, String> =
        match qrcodegen::QrCode::encode_text(text, qrcodegen::QrCodeEcc::Medium) {
            Ok(qr) => Ok(qr),
            Err(err) => Err(err.to_string()),
        };

    if qr.is_err() {
        return Err(qr.err().unwrap());
    }

    let code = qr?;

    // "+ 8 * 8" is here to add padding (the white border around the QRCode)
    // As some QRCode readers don't work without padding
    let image_size = (code.size() as u32) * 8 + 8 * 8;

    let canvas = get_qr_draw_canvas(code);

    // Encode the canvas into a PNG
    let encoder = image::codecs::png::PngEncoder::new(&mut vec);
    match encoder.write_image(
        &canvas.into_raw(),
        image_size,
        image_size,
        image::ColorType::L8,
    ) {
        Ok(_) => Ok(vec),
        Err(err) => Err(err.to_string()),
    }
}

/// Convert text to a base64 encoded PNG QR code.
pub fn qr_base64(text: &str) -> Result<String, String> {
    use base64::{engine::general_purpose, Engine as _};
    Ok(qr_png(text).map(|vec| general_purpose::STANDARD.encode(vec))?)
}

/// Will return a qrcode to automatically add a TOTP as a base64 string. Needs feature `qr` to be enabled!
/// Result will be in the form of a string containing a base64-encoded png, which you can embed in HTML without needing
/// To store the png as a file.
///
/// # Errors
///
/// This will return an error in case the URL gets too long to encode into a QR code.
/// This would require the get_url method to generate an url bigger than 2000 characters,
/// Which would be too long for some browsers anyway.
///
/// It will also return an error in case it can't encode the qr into a png. This shouldn't happen unless either the qrcode library returns malformed data, or the image library doesn't encode the data correctly
impl TOTP {
    pub fn get_qr(&self) -> Result<String, String> {
        let url = self.get_url();
        qr_base64(&url)
    }
}
thodg/totp-rs/src/qr.rs

Commit

src/qr.rs
