local conversion

bincio/extract/simplify.py

@@ -2,11 +2,51 @@
 
 from typing import Optional
 
-from rdp import rdp
-
 from bincio.extract.models import DataPoint
 
 
+def _rdp_mask(coords: list[list[float]], epsilon: float) -> list[bool]:
+    """Pure-Python RDP — returns a boolean keep-mask of the same length as coords."""
+    n = len(coords)
+    if n < 2:
+        return [True] * n
+
+    mask = [False] * n
+    mask[0] = mask[-1] = True
+
+    stack = [(0, n - 1)]
+    while stack:
+        start, end = stack.pop()
+        if end - start < 2:
+            continue
+        x1, y1 = coords[start]
+        x2, y2 = coords[end]
+        dx, dy = x2 - x1, y2 - y1
+        seg_len_sq = dx * dx + dy * dy
+
+        max_dist = -1.0
+        max_idx = start + 1
+        for i in range(start + 1, end):
+            x0, y0 = coords[i]
+            if seg_len_sq == 0:
+                d = ((x0 - x1) ** 2 + (y0 - y1) ** 2) ** 0.5
+            else:
+                t = ((x0 - x1) * dx + (y0 - y1) * dy) / seg_len_sq
+                t = max(0.0, min(1.0, t))
+                px, py = x1 + t * dx, y1 + t * dy
+                d = ((x0 - px) ** 2 + (y0 - py) ** 2) ** 0.5
+            if d > max_dist:
+                max_dist = d
+                max_idx = i
+
+        if max_dist >= epsilon:
+            mask[max_idx] = True
+            stack.append((start, max_idx))
+            stack.append((max_idx, end))
+
+    return mask
+
+
 def simplify_track(
     points: list[DataPoint],
     epsilon: float = 0.0001,
@@ -21,7 +61,7 @@ def simplify_track(
         return [p for p, _, _ in gps_pts]
 
     coords = [[lon, lat] for _, lat, lon in gps_pts]
-    mask = rdp(coords, epsilon=epsilon, return_mask=True)
+    mask = _rdp_mask(coords, epsilon=epsilon)
     return [p for (p, _, _), keep in zip(gps_pts, mask) if keep]
 
 
@@ -40,7 +80,7 @@ def preview_coords(
 
     # Coarse RDP (larger epsilon = fewer points)
     coords = [[lon, lat] for lat, lon in gps]
-    mask = rdp(coords, epsilon=0.001, return_mask=True)
+    mask = _rdp_mask(coords, epsilon=0.001)
     reduced = [gps[i] for i, keep in enumerate(mask) if keep]
 
     # Subsample if still too many — always include last point without exceeding max_points