shard image across threads

src/main.rs

@@ -1,5 +1,4 @@
 use png::{ColorType, Decoder};
-use rand::{thread_rng, Rng};
 use sscanf::sscanf;
 use std::error::Error;
 use std::fs::File;
@@ -8,15 +7,16 @@ use std::net::TcpStream;
 use std::thread;
 
 fn main() -> Result<(), Box<dyn Error>> {
-    let decoder = Decoder::new(File::open("nopslide.png")?);
+    let decoder = Decoder::new(File::open("kame-mosaic.apng")?);
     let mut reader = decoder.read_info()?;
     let mut pixelbuf = vec![0; reader.output_buffer_size()];
     let info = reader.next_frame(&mut pixelbuf)?;
 
     thread::scope(|s| {
-        for _ in 0..32 {
-            s.spawn(|| -> Result<(), Box<dyn Error + Send + Sync>> {
-                let stream = TcpStream::connect("151.217.15.79:1337")?;
+        for i in 0..3 {
+            let pixelbuf = &pixelbuf;
+            s.spawn(move || -> Result<(), Box<dyn Error + Send + Sync>> {
+                let stream = TcpStream::connect("151.217.15.90:1337")?;
                 // disable Nagle's algorithm
                 stream.set_nodelay(true)?;
                 let mut reader = BufReader::new(stream.try_clone()?);
@@ -28,16 +28,27 @@ fn main() -> Result<(), Box<dyn Error>> {
                 // XXX sscanf does not like \n after numbers ... O_o
                 // XXX sscanf returns Result<(), Box<dyn Error>> which is not + Send + Sync
                 let size = sscanf!(&buf[..buf.len() - 1], "SIZE {u32} {u32}").unwrap();
+                println!("SIZE {} {}", size.0, size.1);
 
-                let mut rng = thread_rng();
+                let pos = ((size.0 - info.width) / 2, (size.1 - info.height) / 2);
                 loop {
-                    let pos = (
-                        rng.gen_range(0..size.0 - info.width),
-                        rng.gen_range(0..size.1 - info.height),
-                    );
-                    for x in 0..info.width {
-                        for y in 0..info.height {
+                    for y in (i..info.height).step_by(3) {
+                        for x in 0..info.width {
                             match info.color_type {
+                                ColorType::Rgba => {
+                                    let offset = ((x + y * info.width) * 4) as usize;
+                                    if pixelbuf[offset + 3] != 0 {
+                                        write!(
+                                            writer,
+                                            "PX {} {} {:02x}{:02x}{:02x}\n",
+                                            x + pos.0,
+                                            y + pos.1,
+                                            pixelbuf[offset],
+                                            pixelbuf[offset + 1],
+                                            pixelbuf[offset + 2]
+                                        )?;
+                                    }
+                                }
                                 ColorType::GrayscaleAlpha => {
                                     let offset = ((x + y * info.width) * 2) as usize;
                                     if pixelbuf[offset + 1] != 0 {