feat: min_recall - Halcon-style feature recall check post-refine

_compute_recall calcola hits/N feature template alla pose finale
(post sub-pixel refine). Equivalente Halcon MinScore originale:
quante feature shape effettivamente combaciano sul match accettato.

Param min_recall (default 0 = off, backward compat). Util quando
NCC e' alto ma poche feature reali matchano (es. match parziale
su zona di simil-tessitura). Soglia 0.7-0.9 raccomandata per
filtri stringenti.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pm2d/line_matcher.py

@@ -740,6 +740,63 @@ class LineShapeMatcher:
                 s2, cx2, cy2 = _score_at_angle(x2)
         return best
 
+    def _compute_recall(
+        self, spread0: np.ndarray, variant: _Variant,
+        cx: float, cy: float, angle_deg: float,
+    ) -> float:
+        """Frazione di feature template che combaciano nello spread scena
+        alla pose (cx, cy, angle, variant.scale).
+
+        Riusa template_gray + warp per estrarre features alla pose esatta
+        (vs feature pre-computate alla pose della variante grezza). Ritorna
+        hits/N in [0, 1]. Halcon-equivalent: questo e' il "MinScore" originale.
+        """
+        if self.template_gray is None:
+            return 1.0
+        h, w = self.template_gray.shape
+        scale = variant.scale
+        sw = max(16, int(round(w * scale)))
+        sh = max(16, int(round(h * scale)))
+        gray_s = cv2.resize(self.template_gray, (sw, sh), interpolation=cv2.INTER_LINEAR)
+        mask_src = (
+            self._train_mask if self._train_mask is not None
+            else np.full_like(self.template_gray, 255)
+        )
+        mask_s = cv2.resize(mask_src, (sw, sh), interpolation=cv2.INTER_NEAREST)
+        diag = int(np.ceil(np.hypot(sh, sw))) + 6
+        py = (diag - sh) // 2; px = (diag - sw) // 2
+        gray_p = cv2.copyMakeBorder(
+            gray_s, py, diag - sh - py, px, diag - sw - px, cv2.BORDER_REPLICATE,
+        )
+        mask_p = cv2.copyMakeBorder(
+            mask_s, py, diag - sh - py, px, diag - sw - px,
+            cv2.BORDER_CONSTANT, value=0,
+        )
+        center = (diag / 2.0, diag / 2.0)
+        M = cv2.getRotationMatrix2D(center, angle_deg, 1.0)
+        gray_r = cv2.warpAffine(gray_p, M, (diag, diag),
+                                 flags=cv2.INTER_LINEAR,
+                                 borderMode=cv2.BORDER_REPLICATE)
+        mask_r = cv2.warpAffine(mask_p, M, (diag, diag),
+                                 flags=cv2.INTER_NEAREST, borderValue=0)
+        mag, bins = self._gradient(gray_r)
+        fx, fy, fb = self._extract_features(mag, bins, mask_r)
+        n_feat = len(fx)
+        if n_feat < 4:
+            return 0.0
+        H, W = spread0.shape
+        spread_dtype = spread0.dtype.type
+        ix = int(round(cx)); iy = int(round(cy))
+        hits = 0
+        for i in range(n_feat):
+            xs = ix + int(fx[i] - center[0])
+            ys = iy + int(fy[i] - center[1])
+            if 0 <= xs < W and 0 <= ys < H:
+                bit = spread_dtype(1 << int(fb[i]))
+                if spread0[ys, xs] & bit:
+                    hits += 1
+        return hits / n_feat
+
     def _verify_ncc(
         self, scene_gray: np.ndarray, cx: float, cy: float,
         angle_deg: float, scale: float,
@@ -828,6 +885,7 @@ class LineShapeMatcher:
         greediness: float = 0.0,
         batch_top: bool = False,
         nms_iou_threshold: float = 0.3,
+        min_recall: float = 0.0,
     ) -> list[Match]:
         """
         scale_penalty: se > 0, riduce lo score per match a scala diversa da 1.0:
@@ -1195,6 +1253,17 @@ class LineShapeMatcher:
             if float(score_f) < min_score:
                 continue
 
+            # Feature recall (Halcon MinScore-style): conta quante feature
+            # template effettivamente combaciano nello spread scena alla
+            # pose finale. Scarta se sotto min_recall (default 0 = off).
+            # Util contro match parziali ad alto NCC ma poche feature reali.
+            if min_recall > 0.0:
+                recall = self._compute_recall(
+                    spread0, var, cx_f, cy_f, ang_f,
+                )
+                if recall < min_recall:
+                    continue
+
             # Ri-traslo coord da spazio crop ROI a spazio scena originale.
             cx_out = cx_f + roi_offset[0]
             cy_out = cy_f + roi_offset[1]