implement replacement rules for cleaning up and normalizing plates

frigate/config/classification.py

@@ -217,6 +217,13 @@ class CameraFaceRecognitionConfig(FrigateBaseModel):
     model_config = ConfigDict(extra="forbid", protected_namespaces=())
 
 
+class ReplaceRule(FrigateBaseModel):
+    pattern: str = Field(..., title="Regex pattern to match.")
+    replacement: str = Field(
+        ..., title="Replacement string (supports backrefs like '\\1')."
+    )
+
+
 class LicensePlateRecognitionConfig(FrigateBaseModel):
     enabled: bool = Field(default=False, title="Enable license plate recognition.")
     model_size: str = Field(
@@ -269,6 +276,10 @@ class LicensePlateRecognitionConfig(FrigateBaseModel):
         title="The device key to use for LPR.",
         description="This is an override, to target a specific device. See https://onnxruntime.ai/docs/execution-providers/ for more information",
     )
+    replace_rules: List[ReplaceRule] = Field(
+        default_factory=list,
+        title="List of regex replacement rules for normalizing detected plates. Each rule has 'pattern' and 'replacement'.",
+    )
 
 
 class CameraLicensePlateRecognitionConfig(FrigateBaseModel):

frigate/data_processing/common/license_plate/mixin.py

@@ -360,6 +360,27 @@ class LicensePlateProcessingMixin:
                 conf for conf_list in qualifying_confidences for conf in conf_list
             ]
 
+            # Apply replace rules to combined_plate if configured
+            original_combined = combined_plate
+            if self.lpr_config.replace_rules:
+                for rule in self.lpr_config.replace_rules:
+                    try:
+                        pattern = getattr(rule, "pattern", "")
+                        replacement = getattr(rule, "replacement", "")
+                        if pattern:
+                            combined_plate = re.sub(
+                                pattern, replacement, combined_plate
+                            )
+                    except re.error as e:
+                        logger.warning(
+                            f"{camera}: Invalid regex in replace_rules '{pattern}': {e}"
+                        )
+
+            if combined_plate != original_combined:
+                logger.debug(
+                    f"{camera}: Rules applied: '{original_combined}' -> '{combined_plate}'"
+                )
+
             # Compute the combined area for qualifying boxes
             qualifying_boxes = [boxes[i] for i in qualifying_indices]
             qualifying_plate_images = [