feat: generate RGB(A) image based on intensity

src/main.rs

@@ -3,7 +3,7 @@ mod data;
 use data::Rv;
 
 use image::imageops;
-use image::GrayAlphaImage;
+use image::RgbaImage;
 
 use proj::Proj;
 
@@ -12,23 +12,41 @@ use std::io::BufReader;
 
 const PROJ_WGS84_DE1200: &'static str = "+proj=stere +lat_0=90 +lat_ts=60 +lon_0=10 +a=6378137 +b=6356752.3142451802 +no_defs +x_0=543196.83521776402 +y_0=3622588.8619310018";
 
+#[repr(u32)]
+enum Intensity {
+    None = 0xffffff00,
+    Light = 0x80d0d080,
+    Moderate = 0x50a0e080,
+    Heavy = 0x1030f080,
+    Unknown = 0xd0d0d080,
+}
+
 fn main() {
     let rv = Rv::parse(BufReader::new(File::open("input").unwrap())).unwrap();
     rv.expect_version(5).unwrap();
 
-    let mut data = Vec::with_capacity(1100 * 1200 * 2);
+    let mut data = Vec::with_capacity(1100 * 1200 * 4);
 
     for v in rv.data() {
-        if *v == 0x29c4 {
-            data.push(0);
-            data.push(255);
+        let intensity = if *v == 0x29c4 {
+            Intensity::Unknown
         } else {
-            data.push(if *v > 0 { 255 } else { 127 });
-            data.push(255);
+            let mm_per_h = *v as f64 * rv.scale() * 12.0; // 12 * 5 min intervals per hour
+            if mm_per_h < 0.1 {
+                Intensity::None
+            } else if mm_per_h < 5.0 {
+                Intensity::Light
+            } else if mm_per_h < 15.0 {
+                Intensity::Moderate
+            } else {
+                Intensity::Heavy
             }
+        };
+
+        data.extend_from_slice(&(intensity as u32).to_be_bytes());
     }
 
-    let mut img = GrayAlphaImage::from_raw(1100, 1200, data).unwrap();
+    let mut img = RgbaImage::from_raw(1100, 1200, data).unwrap();
     imageops::flip_vertical_in_place(&mut img);
     img.save("rv.png").unwrap();