fix(scripts): guard zero-division in vectorize summarise aggregate (#299)

backend/scripts/spike_plan_vectorize.py

@@ -93,9 +93,7 @@ def _require_binary(name: str) -> str:
     path = shutil.which(name)
     if path is None:
         logger.error("required binary %r not found on PATH", name)
-        raise SystemExit(
+        raise SystemExit(f"{name!r} not found — install it (e.g. `brew install {name}`) and retry")
-            f"{name!r} not found — install it (e.g. `brew install {name}`) and retry"
-        )
     return path
 
 
@@ -145,9 +143,13 @@ def svg_to_png(rsvg_bin: str, svg_path: Path, png_path: Path, *, width: int) ->
     try:
         subprocess.run(
             [
-                rsvg_bin, "-w", str(width),
+                rsvg_bin,
+                "-w",
+                str(width),
                 "--background-color=white",
-                "-o", str(png_path), str(svg_path),
+                "-o",
+                str(png_path),
+                str(svg_path),
             ],
             check=True,
             capture_output=True,
@@ -216,8 +218,10 @@ def summarise(results: list[VectorizeResult]) -> None:
     print(f"max ratio     : {max(ratios):.2f}x")
     total_raster = sum(r.raster_bytes for r in results)
     total_svg = sum(r.svg_bytes for r in results)
-    print(f"aggregate     : {total_raster}B raster -> {total_svg}B svg "
+    agg_ratio = total_raster / total_svg if total_svg else float("inf")
-          f"({total_raster / total_svg:.2f}x overall)")
+    print(
+        f"aggregate     : {total_raster}B raster -> {total_svg}B svg " f"({agg_ratio:.2f}x overall)"
+    )
 
 
 def build_parser() -> argparse.ArgumentParser:
@@ -225,27 +229,37 @@ def build_parser() -> argparse.ArgumentParser:
         description="Spike: contour-vectorize floor-plan rasters (PNG/JPG → SVG) via Potrace.",
     )
     parser.add_argument(
-        "--in-dir", type=Path, required=True,
+        "--in-dir",
+        type=Path,
+        required=True,
         help="folder containing input rasters (PNG/JPG/...)",
     )
     parser.add_argument(
-        "--out-dir", type=Path, required=True,
+        "--out-dir",
+        type=Path,
+        required=True,
         help="folder for output .pbm/.svg (and .rendered.png with --render-back)",
     )
     parser.add_argument(
-        "--threshold", type=int, default=128,
+        "--threshold",
+        type=int,
+        default=128,
         help="grayscale ink/paper cutoff 0-255 (default 128)",
     )
     parser.add_argument(
-        "--invert", action="store_true",
+        "--invert",
+        action="store_true",
         help="treat light strokes on a dark field as ink",
     )
     parser.add_argument(
-        "--render-back", action="store_true",
+        "--render-back",
+        action="store_true",
         help="rasterise each SVG back to PNG via rsvg-convert for visual QA",
     )
     parser.add_argument(
-        "--render-width", type=int, default=900,
+        "--render-width",
+        type=int,
+        default=900,
         help="width in px for --render-back output (default 900)",
     )
     return parser