Add animated GIF output with parallelised frame quantization

Render an animated clct_animation.gif alongside the per-step PNGs.
Frames are loaded and colour-quantized in parallel via rayon, then
written sequentially with the gif crate.  Also converts timestamps
to CET/CEST using chrono-tz.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -127,6 +127,12 @@ version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
 
+[[package]]
+name = "byteorder-lite"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f1fe948ff07f4bd06c30984e69f5b4899c516a3ef74f34df92a2df2ab535495"
+
 [[package]]
 name = "bytes"
 version = "1.11.1"
@@ -186,6 +192,16 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "chrono-tz"
+version = "0.10.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a6139a8597ed92cf816dfb33f5dd6cf0bb93a6adc938f11039f371bc5bcd26c3"
+dependencies = [
+ "chrono",
+ "phf",
+]
+
 [[package]]
 name = "clap"
 version = "4.5.60"
@@ -233,8 +249,11 @@ dependencies = [
  "anyhow",
  "bzip2",
  "chrono",
+ "chrono-tz",
  "clap",
  "font8x8",
+ "gif",
+ "image 0.25.9",
  "plotters",
  "rayon",
  "reqwest",
@@ -438,6 +457,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "gif"
+version = "0.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f5df2ba84018d80c213569363bdcd0c64e6933c67fe4c1d60ecf822971a3c35e"
+dependencies = [
+ "color_quant",
+ "weezl",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.15.5"
@@ -692,7 +721,20 @@ dependencies = [
  "color_quant",
  "jpeg-decoder",
  "num-traits",
- "png",
+ "png 0.17.16",
+]
+
+[[package]]
+name = "image"
+version = "0.25.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6506c6c10786659413faa717ceebcb8f70731c0a60cbae39795fdf114519c1a"
+dependencies = [
+ "bytemuck",
+ "byteorder-lite",
+ "moxcms",
+ "num-traits",
+ "png 0.18.1",
 ]
 
 [[package]]
@@ -790,6 +832,16 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "moxcms"
+version = "0.7.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac9557c559cd6fc9867e122e20d2cbefc9ca29d80d027a8e39310920ed2f0a97"
+dependencies = [
+ "num-traits",
+ "pxfm",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -817,6 +869,24 @@ version = "2.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
+[[package]]
+name = "phf"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "913273894cec178f401a31ec4b656318d95473527be05c0752cc41cdc32be8b7"
+dependencies = [
+ "phf_shared",
+]
+
+[[package]]
+name = "phf_shared"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06005508882fb681fd97892ecff4b7fd0fee13ef1aa569f8695dae7ab9099981"
+dependencies = [
+ "siphasher",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.17"
@@ -860,7 +930,7 @@ version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72ce181e3f6bf82d6c1dc569103ca7b1bd964c60ba03d7e6cdfbb3e3eb7f7405"
 dependencies = [
- "image",
+ "image 0.24.9",
  "plotters-backend",
 ]
 
@@ -877,6 +947,19 @@ dependencies = [
  "miniz_oxide",
 ]
 
+[[package]]
+name = "png"
+version = "0.18.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60769b8b31b2a9f263dae2776c37b1b28ae246943cf719eb6946a1db05128a61"
+dependencies = [
+ "bitflags 2.11.0",
+ "crc32fast",
+ "fdeflate",
+ "flate2",
+ "miniz_oxide",
+]
+
 [[package]]
 name = "potential_utf"
 version = "0.1.4"
@@ -904,6 +987,12 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "pxfm"
+version = "0.1.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5a041e753da8b807c9255f28de81879c78c876392ff2469cde94799b2896b9d"
+
 [[package]]
 name = "quinn"
 version = "0.11.9"
@@ -1203,6 +1292,12 @@ version = "0.3.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e320a6c5ad31d271ad523dcf3ad13e2767ad8b1cb8f047f75a8aeaf8da139da2"
 
+[[package]]
+name = "siphasher"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2aa850e253778c88a04c3d7323b043aeda9d3e30d5971937c1855769763678e"
+
 [[package]]
 name = "slab"
 version = "0.4.12"
@@ -1573,6 +1668,12 @@ dependencies = [
  "rustls-pki-types",
 ]
 
+[[package]]
+name = "weezl"
+version = "0.1.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a28ac98ddc8b9274cb41bb4d9d4d5c425b6020c50c46f25559911905610b4a88"
+
 [[package]]
 name = "windows-core"
 version = "0.62.2"

Cargo.toml

@@ -17,3 +17,6 @@ chrono   = { version = "0.4", default-features = false, features = ["std", "cloc
 anyhow   = "1"
 spade    = "2"
 rayon    = "1"
+image    = { version = "0.25", default-features = false, features = ["png"] }
+gif      = "0.14"
+chrono-tz = "0.10.4"

src/main.rs

@@ -139,14 +139,15 @@ fn main() -> Result<()> {
         }
 
         let forecast_dt = dt + chrono::Duration::hours(step as i64);
+        let forecast_dt = forecast_dt.with_timezone(&chrono_tz::Europe::Berlin);
         let title = if step == 0 {
             format!(
-                "Conditions at {} UTC",
+                "Conditions at {} CET",
                 forecast_dt.format("%Y-%m-%d %H:%M")
             )
         } else {
             format!(
-                "Prediction at {} UTC (+{:02}h)",
+                "Prediction at {} CET (+{:02}h)",
                 forecast_dt.format("%Y-%m-%d %H:%M"),
                 step
             )
@@ -167,6 +168,47 @@ fn main() -> Result<()> {
         eprintln!("  {}", p.display());
     }
 
+    if output_paths.len() > 1 {
+        eprintln!("Building animation...");
+        let gif_path = cache_dir.join("clct_animation.gif");
+        create_gif(&output_paths, &gif_path).context("Creating GIF")?;
+        eprintln!("  GIF: {}", gif_path.display());
+    }
+
+    Ok(())
+}
+
+fn create_gif(png_paths: &[PathBuf], out_path: &PathBuf) -> Result<()> {
+    use gif::{Encoder, Frame, Repeat};
+
+    // Load PNGs and quantize to 256-colour palettes in parallel (the bottleneck).
+    let n = png_paths.len();
+    let frames: Vec<Frame<'static>> = png_paths
+        .par_iter()
+        .enumerate()
+        .map(|(i, path)| -> Result<Frame<'static>> {
+            let img = image::open(path)
+                .with_context(|| format!("Loading PNG {}", path.display()))?
+                .into_rgba8();
+            let (width, height) = img.dimensions();
+            let mut pixels = img.into_raw();
+            // speed 8: slightly better quality than the default (10)
+            let mut frame =
+                Frame::from_rgba_speed(width as u16, height as u16, &mut pixels, 8);
+            // Pause longer on first and last frame; 1 unit = 10 ms
+            frame.delay = if i == 0 || i == n - 1 { 200 } else { 40 };
+            Ok(frame)
+        })
+        .collect::<Result<Vec<_>>>()?;
+
+    // Write frames sequentially (GIF encoder is not thread-safe).
+    let file = std::fs::File::create(out_path)?;
+    let (w, h) = (frames[0].width, frames[0].height);
+    let mut encoder = Encoder::new(file, w, h, &[])?;
+    encoder.set_repeat(Repeat::Infinite)?;
+    for frame in &frames {
+        encoder.write_frame(frame)?;
+    }
     Ok(())
 }