add qr module

src/lib.rs

@@ -0,0 +1 @@
+mod qr;

src/main.rs

@@ -58,7 +58,7 @@ impl eframe::App for Flasher {
                 .build()
                 .unwrap();
             let bytes = ImageBuilder::default()
-                .fit_width(1200)
+                .fit_width(1100)
                 .to_pixmap(&qr)
                 .encode_png()
                 .unwrap();

src/qr.rs

@@ -0,0 +1,38 @@
+use fast_qr::ECL;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Mode {
+    Ascii,
+    Binary,
+}
+
+pub fn get_size(len: usize, mode: Mode) -> usize {
+    if mode == Mode::Ascii {
+        // alphanumeric mode is only 5.5 bits per character, so 5.5 / 8 = 0.6875
+        (len as f64 * 0.6875).ceil() as usize
+    } else {
+        len
+    }
+}
+
+pub fn choose_version(size: usize, ecl: ECL) -> fast_qr::Version {
+    use fast_qr::Version::*;
+    let ecl = match ecl {
+        ECL::L => 0.7,
+        ECL::M => 0.15,
+        ECL::Q => 0.25,
+        ECL::H => 0.30,
+    };
+
+    let size = (size as f64 / ecl) as usize;
+
+    match size {
+        0..=7 => V01,
+        8..=14 => V02,
+        15..=24 => V03,
+        25..=78 => V04,
+
+        //
+        _ => V40,
+    }
+}