QR Code scan using rqrr rust.

rqrr_helper.rs

/// Scan current video frame for a valid QR code containing customer id, returning it if found.
    fn process_frame(&self) -> anyhow::Result<Option<i32>> {
        // Get necessary elements
        let video = self
            .ref_video
            .cast::<HtmlVideoElement>()
            .ok_or(anyhow!("Video required"))?;
        let context = self.context.as_ref().ok_or(anyhow!("Context required"))?;
        let (width, height) = self.camera_dim;
        // Draw frame to canvas
        context
            .draw_image_with_html_video_element_and_dw_and_dh(
                &video,
                0.0,
                0.0,
                width as f64,
                height as f64,
            )
            .map_err(|e| anyhow!("{:?}", e))?;
        // Get frame data
        let frame = context
            .get_image_data(0.0, 0.0, width as f64, height as f64)
            .map_err(|e| anyhow!("{:?}", e))?
            .data()
            .0;
        // Scan image data for a QR code
        let image: image::RgbaImage =
            image::ImageBuffer::from_vec(width as u32, height as u32, frame)
                .ok_or(anyhow!("Error creating image buffer"))?;
        let image = image::DynamicImage::ImageRgba8(image);
        // rqrr will sometimes panic, so we need to catch it.
        // See https://github.com/WanzenBug/rqrr/issues/3
        std::panic::catch_unwind(|| {
            let mut results = rqrr::PreparedImage::prepare(image.to_luma8());
            for result in results.detect_grids().into_iter() {
                // If a QR code is found and it can be parsed into a user ID, return it without
                // looking at any other results.
                if let Ok(Ok(id)) = result.decode().map(|(_, r)| r.parse::<i32>()) {
                    return Ok(Some(id));
                }
            }

            Ok(None)
        })
        .map_err(|e| anyhow!("rqrr error: {:?}", e))?
    }