first pass of merging in warp (doesn't build)

app/src/drive/sharing/qr_code.rs

@@ -0,0 +1,74 @@
+use std::io::Cursor;
+
+use image::{ImageBuffer, ImageFormat, Luma};
+use qrcode::{Color, QrCode};
+
+pub const QUIET_ZONE_MODULES: usize = 4;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct QrMatrix {
+    width: usize,
+    modules: Vec<bool>,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum QrCodeError {
+    #[error("Unable to encode QR code")]
+    Encode,
+    #[error("Unable to encode QR code image")]
+    Image(#[from] image::ImageError),
+}
+
+impl QrMatrix {
+    pub fn width(&self) -> usize {
+        self.width
+    }
+
+    pub fn is_dark(&self, x: usize, y: usize) -> bool {
+        self.modules
+            .get(y.saturating_mul(self.width).saturating_add(x))
+            .copied()
+            .unwrap_or(false)
+    }
+}
+
+pub fn qr_matrix_for_url(url: &str) -> Result<QrMatrix, QrCodeError> {
+    let code = QrCode::new(url.as_bytes()).map_err(|_| QrCodeError::Encode)?;
+    let width = code.width();
+    let modules = code
+        .to_colors()
+        .into_iter()
+        .map(|color| matches!(color, Color::Dark))
+        .collect();
+    Ok(QrMatrix { width, modules })
+}
+
+pub fn qr_png_for_url(url: &str, pixel_size: u32) -> Result<Vec<u8>, QrCodeError> {
+    let matrix = qr_matrix_for_url(url)?;
+    let modules_with_quiet_zone = matrix.width().saturating_add(QUIET_ZONE_MODULES * 2);
+    let module_size = (pixel_size as usize / modules_with_quiet_zone).max(1);
+    let image_size = modules_with_quiet_zone.saturating_mul(module_size) as u32;
+    let mut image = ImageBuffer::from_pixel(image_size, image_size, Luma([255u8]));
+
+    for y in 0..matrix.width() {
+        for x in 0..matrix.width() {
+            if matrix.is_dark(x, y) {
+                let start_x = (x + QUIET_ZONE_MODULES) * module_size;
+                let start_y = (y + QUIET_ZONE_MODULES) * module_size;
+                for pixel_y in start_y..start_y + module_size {
+                    for pixel_x in start_x..start_x + module_size {
+                        image.put_pixel(pixel_x as u32, pixel_y as u32, Luma([0u8]));
+                    }
+                }
+            }
+        }
+    }
+
+    let mut png = Cursor::new(Vec::new());
+    image.write_to(&mut png, ImageFormat::Png)?;
+    Ok(png.into_inner())
+}
+
+#[cfg(test)]
+#[path = "qr_code_tests.rs"]
+mod tests;