First image has been generated!

src/grid.rs

@@ -63,6 +63,23 @@ impl Grid {
         self.blur
             .run(&mut self.data, &mut self.buf, radius as f32, decay_factor);
     }
+
+    pub fn quantile(&self, fraction: f32) -> f32 {
+        let index = if fraction == 1.0 {
+            self.data.len() - 1
+        } else {
+            (self.data.len() as f32 * fraction) as usize
+        };
+        let mut sorted = self.data.clone();
+        sorted
+            .as_mut_slice()
+            .select_nth_unstable_by(index, |a, b| a.partial_cmp(b).unwrap());
+        sorted[index]
+    }
+
+    pub fn data(&self) -> &[f32] {
+        &self.data
+    }
 }
 
 #[cfg(test)]

src/main.rs

@@ -1,10 +1,9 @@
 use physarum::model;
 
 fn main() {
-    let mut model = model::Model::new(4, 4, 20, 1);
+    let mut model = model::Model::new(128, 128, 4096, 1);
     println!("{:#?}", model);
     model.step();
-    println!("{:#?}", model);
     model.step();
-    println!("{:#?}", model);
+    model.save_to_image();
 }

src/model.rs

@@ -176,4 +176,18 @@ impl Model {
             .diffuse(self.diffusivity, self.config.decay_factor);
         self.iteration += 1;
     }
+
+    /// Output the current trail layer as a grayscale image.
+    pub fn save_to_image(&self) {
+        let mut img = image::GrayImage::new(self.width as u32, self.height as u32);
+        let max_value = self.grid.quantile(0.999);
+
+        for (i, value) in self.grid.data().iter().enumerate() {
+            let x = (i % self.width) as u32;
+            let y = (i / self.width) as u32;
+            let c = (value / max_value).clamp(0.0, 1.0) * 255.0;
+            img.put_pixel(x, y, image::Luma([c as u8]));
+        }
+        img.save("out.png").unwrap();
+    }
 }