fix: add MapLibre retina sprite builder

tools/cm95_maplibre_retina_sprite.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+from __future__ import annotations
+
+import argparse
+import json
+from pathlib import Path
+import shutil
+import subprocess
+from typing import Any
+
+
+def _scale_pair_list(value: Any, factor: int) -> Any:
+    if not isinstance(value, list):
+        return value
+    out = []
+    for item in value:
+        if isinstance(item, list) and len(item) == 2:
+            out.append([item[0] * factor, item[1] * factor])
+        else:
+            out.append(item)
+    return out
+
+
+def _retina_entry(entry: dict[str, Any], factor: int) -> dict[str, Any]:
+    out = dict(entry)
+    for key in ("x", "y", "width", "height"):
+        if key in out:
+            out[key] = int(out[key]) * factor
+    if isinstance(out.get("content"), list) and len(out["content"]) == 4:
+        out["content"] = [v * factor for v in out["content"]]
+    for key in ("stretchX", "stretchY"):
+        if key in out:
+            out[key] = _scale_pair_list(out[key], factor)
+    out["pixelRatio"] = factor
+    return out
+
+
+def build_retina(prefix: Path, *, factor: int = 2) -> dict[str, Any]:
+    src_png = prefix.with_suffix(".png")
+    src_json = prefix.with_suffix(".json")
+    if not src_png.is_file() or not src_json.is_file():
+        raise FileNotFoundError(f"missing sprite pair for prefix {prefix}")
+    if shutil.which("convert") is None:
+        raise RuntimeError("ImageMagick convert is required")
+
+    dst_png = prefix.with_name(prefix.name + f"@{factor}x").with_suffix(".png")
+    dst_json = prefix.with_name(prefix.name + f"@{factor}x").with_suffix(".json")
+    data = json.loads(src_json.read_text(encoding="utf-8"))
+    retina = {name: _retina_entry(dict(entry), factor) for name, entry in data.items()}
+
+    subprocess.run(
+        ["convert", str(src_png), "-filter", "point", "-resize", f"{factor * 100}%", str(dst_png)],
+        check=True,
+    )
+    dst_json.write_text(json.dumps(retina, ensure_ascii=False, indent=2) + "\n", encoding="utf-8")
+    return {
+        "prefix": str(prefix),
+        "entry_count": len(retina),
+        "png": str(dst_png),
+        "json": str(dst_json),
+        "pixel_ratio": factor,
+    }
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description="Build MapLibre @2x sprite assets from a 1x sprite pair.")
+    ap.add_argument("prefix", nargs="+", type=Path)
+    args = ap.parse_args()
+    result = [build_retina(prefix) for prefix in args.prefix]
+    print(json.dumps(result, ensure_ascii=False, indent=2))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())