feat: embed gf3 water extraction workflow

backend/app/processors/gf3_water/dltb.py

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+"""DLTB land-use prior definitions.
+
+DLTB should be treated as a soft background layer for flood-period mapping:
+it can change interpretation and confidence, but should not hard-exclude strong
+water evidence outside normal water classes.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field as dc_field
+from pathlib import Path
+
+import numpy as np
+from shapely.geometry import box, shape
+from shapely.ops import transform as shapely_transform
+
+try:
+    import fiona
+except Exception:  # pragma: no cover - optional at runtime
+    fiona = None
+
+try:
+    from pyproj import Transformer
+except Exception:  # pragma: no cover - optional at runtime
+    Transformer = None
+
+
+@dataclass(frozen=True)
+class DltbConfig:
+    gdb: Path
+    layer: str = "DLTB"
+    field: str = "DLMC"
+    mode: str = "soft"
+    max_features: int | None = None
+    water_names: tuple[str, ...] = dc_field(default_factory=lambda: ("河流水面", "湖泊水面", "水库水面", "坑塘水面", "沟渠"))
+    paddy_names: tuple[str, ...] = dc_field(default_factory=lambda: ("水田",))
+    strict_names: tuple[str, ...] = dc_field(default_factory=lambda: ("城镇村道路用地", "公路用地", "农村道路", "设施农用地"))
+
+
+@dataclass
+class DltbSceneZones:
+    water_geoms: list
+    paddy_geoms: list
+    strict_geoms: list
+    normal_geoms: list
+    feature_count: int
+    class_counts: dict[str, int]
+    dlmc_values: list[str]
+    crs: str | None
+
+
+def classify_dlmc(name: str, config: DltbConfig) -> str:
+    """Classify one DLMC value into a soft policy zone."""
+    value = (name or "").strip()
+    if value in config.water_names:
+        return "water_prior"
+    if value in config.paddy_names:
+        return "paddy"
+    if value in config.strict_names:
+        return "strict_review"
+    return "normal"
+
+
+def _transform_bounds(bounds: tuple[float, float, float, float], src_crs: str, dst_crs) -> tuple[float, float, float, float]:
+    if Transformer is None:
+        raise RuntimeError("pyproj is required to use DLTB priors with CRS transformation")
+    transformer = Transformer.from_crs(src_crs, dst_crs, always_xy=True)
+    left, bottom, right, top = bounds
+    xs = [left, left, right, right]
+    ys = [bottom, top, bottom, top]
+    tx, ty = transformer.transform(xs, ys)
+    return min(tx), min(ty), max(tx), max(ty)
+
+
+def _transform_geom(geom, src_crs, dst_crs: str):
+    if Transformer is None:
+        raise RuntimeError("pyproj is required to transform DLTB geometries")
+    transformer = Transformer.from_crs(src_crs, dst_crs, always_xy=True)
+    return shapely_transform(lambda x, y, z=None: transformer.transform(np.asarray(x), np.asarray(y)), geom)
+
+
+def load_dltb_scene_zones(config: DltbConfig, sar_bounds_wgs84: tuple[float, float, float, float]) -> DltbSceneZones:
+    """Load only DLTB features intersecting one SAR scene.
+
+    The input bounds are WGS84 lon/lat. Returned geometries are transformed to
+    WGS84 and clipped to the SAR bounds.
+    """
+    if fiona is None:
+        raise RuntimeError("fiona is required for DLTB geodatabase access")
+    if not config.gdb.exists():
+        raise FileNotFoundError(f"DLTB geodatabase not found: {config.gdb}")
+
+    roi_wgs84 = box(*sar_bounds_wgs84)
+    water_geoms = []
+    paddy_geoms = []
+    strict_geoms = []
+    normal_geoms = []
+    class_counts = {"water_prior": 0, "paddy": 0, "strict_review": 0, "normal": 0}
+    dlmc_values = set()
+    feature_count = 0
+
+    with fiona.open(config.gdb, layer=config.layer) as src:
+        src_crs = src.crs_wkt or src.crs
+        bbox = sar_bounds_wgs84
+        if src_crs:
+            bbox = _transform_bounds(sar_bounds_wgs84, "EPSG:4326", src_crs)
+
+        for feat in src.filter(bbox=bbox):
+            if config.max_features is not None and feature_count >= config.max_features:
+                break
+            geom_data = feat.get("geometry")
+            if not geom_data:
+                continue
+            geom = shape(geom_data)
+            if geom.is_empty:
+                continue
+            if src_crs:
+                geom = _transform_geom(geom, src_crs, "EPSG:4326")
+            geom = geom.intersection(roi_wgs84)
+            if geom.is_empty:
+                continue
+
+            dlmc = str(feat.get("properties", {}).get(config.field, "") or "").strip()
+            zone = classify_dlmc(dlmc, config)
+            dlmc_values.add(dlmc)
+            class_counts[zone] += 1
+            feature_count += 1
+            if zone == "water_prior":
+                water_geoms.append(geom)
+            elif zone == "paddy":
+                paddy_geoms.append(geom)
+            elif zone == "strict_review":
+                strict_geoms.append(geom)
+            else:
+                normal_geoms.append(geom)
+
+    return DltbSceneZones(
+        water_geoms=water_geoms,
+        paddy_geoms=paddy_geoms,
+        strict_geoms=strict_geoms,
+        normal_geoms=normal_geoms,
+        feature_count=feature_count,
+        class_counts=class_counts,
+        dlmc_values=sorted(v for v in dlmc_values if v),
+        crs=str(src_crs) if "src_crs" in locals() else None,
+    )