optional MtCnn batching (does not work in python3.8)

deepface/models/face_detection/MtCnn.py

@@ -1,4 +1,5 @@
 # built-in dependencies
+import logging
 from typing import List, Union
 
 # 3rd party dependencies
@@ -8,6 +9,8 @@ from mtcnn import MTCNN
 # project dependencies
 from deepface.models.Detector import Detector, FacialAreaRegion
 
+logger = logging.getLogger(__name__)
+
 # pylint: disable=too-few-public-methods
 class MtCnnClient(Detector):
     """
@@ -16,6 +19,7 @@ class MtCnnClient(Detector):
 
     def __init__(self):
         self.model = MTCNN()
+        self.supports_batch_detection = self._supports_batch_detection()
 
     def detect_faces(
         self,
@@ -42,7 +46,10 @@ class MtCnnClient(Detector):
         # mtcnn expects RGB but OpenCV read BGR
         # img_rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
         img_rgb = [img[:, :, ::-1] for img in img]
+        if self.supports_batch_detection:
             detections = self.model.detect_faces(img_rgb)
+        else:
+            detections = [self.model.detect_faces(single_img) for single_img in img_rgb]
 
         for image_detections in detections:
             image_resp = []
@@ -72,3 +79,21 @@ class MtCnnClient(Detector):
         if len(resp) == 1:
             return resp[0]
         return resp
+    
+    def _supports_batch_detection(self) -> bool:
+        import mtcnn
+        try:
+            mtcnn_version = mtcnn.__version__
+        except AttributeError:
+            try:
+                import mtcnn.metadata
+                mtcnn_version = mtcnn.metadata.__version__
+            except AttributeError:
+                logger.warning("Failed to determine mtcnn version")
+                logger.warning("Fallback to single image detection")
+                return False
+        supports_batch_detection = mtcnn_version >= "1.0.0"
+        if not supports_batch_detection:
+            logger.warning("MtCnn version is less than 1.0.0, batch detection is not supported")
+            logger.warning("Fallback to single image detection")
+        return supports_batch_detection