Implement a mp4 renderer

src/render.rs

@@ -1,6 +1,9 @@
 use ansi_term::Color::RGB;
 use crate::{consts, Material as _, SimState};
 use std::fmt::Write as _;
+use std::fs::File;
+use std::path::PathBuf;
+use y4m::{Colorspace, encode, Encoder, Frame, Ratio};
 
 pub struct NumericTermRenderer;
 
@@ -63,6 +66,57 @@ impl ColorTermRenderer {
             }
             write!(&mut buf, "\n");
         }
-        println!("{}\ntime: {:.3e}", buf, state.time());
+        println!("{}\ntime: {:.3e} (fr {})", buf, state.time(), state.step_no());
+    }
+}
+
+pub struct Y4MRenderer {
+    out_path: PathBuf,
+    encoder: Option<Encoder<File>>,
+}
+
+impl Y4MRenderer {
+    pub fn new<S: Into<PathBuf>>(output: S) -> Self {
+        Self {
+            out_path: output.into(),
+            encoder: None,
+        }
+    }
+    pub fn render(&mut self, state: &SimState) {
+        if self.encoder.is_none() {
+            let writer = File::create(&self.out_path).unwrap();
+            self.encoder = Some(encode(state.width(), state.height(), Ratio::new(30, 1))
+                .with_colorspace(Colorspace::C444)
+                .write_header(writer)
+                .unwrap()
+            );
+        }
+
+        let mut pix_y = Vec::new();
+        let mut pix_u = Vec::new();
+        let mut pix_v = Vec::new();
+        for y in 0..state.height() {
+            for x in 0..state.width() {
+                let cell = state.get(x, y);
+                //let r = norm_color(cell.bz() * consts::C);
+                //let r = 0;
+                let r = norm_color(cell.mat().mz()*1.0e-2);
+                let b = (55.0*cell.mat().conductivity()).min(255.0) as u8;
+                //let b = 0;
+                //let b = norm_color(cell.ey());
+                //let g = 0;
+                //let g = norm_color(cell.ex());
+                //let g = norm_color(curl(cell.ex(), cell.ey()));
+                let g = norm_color((cell.bz() * 1.0e4).into());
+                //let g = norm_color(cell.ey().into());
+                pix_y.push(r);
+                pix_u.push(g);
+                pix_v.push(b);
+            }
+        }
+
+        let frame = Frame::new([&*pix_y, &*pix_u, &*pix_v], None);
+        let enc = self.encoder.as_mut().unwrap();
+        enc.write_frame(&frame).unwrap()
     }
 }