thodg/totp-rs/qrcodegen-image/src/lib.rs

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• Hash : c9f1a8b9
  Author :
  Date : 2024-03-08T16:53:40
  

  Update base64 create Signed-off-by: Cléo Rebert <cleo.rebert@gmail.com>

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• qrcodegen-image/src/lib.rs

• //! Utility functions for drawing QR codes generated using `qrcodegen`
  //! to a canvas provided by the `image` crate.
  use image::Luma;
  
  pub use image;
  pub use qrcodegen;
  
  /// Draw a QR code to an image buffer.
  pub fn 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::from_pixel(image_size, image_size, Luma([255]));
  
      let raw = canvas.as_mut();
  
      // The QR inside the white border
      for x_qr in 0..size {
          for y_qr in 0..size {
              if !qr.get_module(x_qr as i32, y_qr as i32) {
                  continue
              }
  
              // 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 y_img in y_start..y_start + 8 {
                  let start = (x_start + y_img * image_size) as usize;
                  raw[start..start + 8].copy_from_slice(&[0; 8]);
              }
          }
      }
      canvas
  }
  
  /// Draw text to a PNG QR code.
  ///     
  /// # 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.
  pub fn draw_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 = 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()),
      }
  }
  
  /// Draw text to a Base64-encoded PNG QR code.
  ///
  /// # 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.
  #[cfg(feature = "base64")]
  pub fn draw_base64(text: &str) -> Result<String, String> {
      use base64::{engine::general_purpose, Engine as _};
      draw_png(text).map(|vec| general_purpose::STANDARD.encode(vec))
  }
  

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