Change calculator's behaviour

- Now clock input stream is optional
- If there are clock stream, always emit count. If not, emit count when vector stream is come in.

mediapipe/calculators/util/counting_vector_size_calculator.h

@@ -39,9 +39,10 @@ template <typename VectorT>
 class CountingVectorSizeCalculator : public CalculatorBase { 
   public:
     static ::mediapipe::Status GetContract(CalculatorContract* cc) {
-        // Check tag.
-        RET_CHECK(cc->Inputs().HasTag("CLOCK"));
+        if (cc->Inputs().HasTag("CLOCK")) {
             cc->Inputs().Tag("CLOCK").SetAny();
+        }
+        
         RET_CHECK(cc->Inputs().HasTag("VECTOR"));
         cc->Inputs().Tag("VECTOR").Set<VectorT>();
         RET_CHECK(cc->Outputs().HasTag("COUNT"));

mediapipe/modules/face_landmark/BUILD

@@ -74,8 +74,8 @@ mediapipe_simple_subgraph(
         "//mediapipe/calculators/image:image_properties_calculator",
         "//mediapipe/calculators/util:association_norm_rect_calculator",
         "//mediapipe/calculators/util:collection_has_min_size_calculator",
-        "//mediapipe/modules/face_detection:face_detection_front_cpu",
         "//mediapipe/calculators/util:counting_vector_size_calculator",
+        "//mediapipe/modules/face_detection:face_detection_front_cpu",
     ],
 )
 
@@ -96,6 +96,7 @@ mediapipe_simple_subgraph(
         "//mediapipe/calculators/image:image_properties_calculator",
         "//mediapipe/calculators/util:association_norm_rect_calculator",
         "//mediapipe/calculators/util:collection_has_min_size_calculator",
+        "//mediapipe/calculators/util:counting_vector_size_calculator",
         "//mediapipe/modules/face_detection:face_detection_front_gpu",
     ],
 )

mediapipe/modules/face_landmark/face_landmark_front_gpu.pbtxt

@@ -43,6 +43,8 @@ output_stream: "ROIS_FROM_LANDMARKS:face_rects_from_landmarks"
 # Regions of interest calculated based on face detections.
 # (std::vector<NormalizedRect>)
 output_stream: "ROIS_FROM_DETECTIONS:face_rects_from_detections"
+# (int)
+output_stream: "FACE_COUNT_FROM_LANDMARKS:face_count"
 
 # Determines if an input vector of NormalizedRect has a size greater than or
 # equal to the provided num_faces.
@@ -189,6 +191,13 @@ node {
   output_stream: "ITERABLE:multi_face_landmarks"
 }
 
+node {
+  calculator: "CountingNormalizedLandmarkListVectorSizeCalculator"
+  input_stream: "CLOCK:image"
+  input_stream: "VECTOR:multi_face_landmarks"
+  output_stream: "COUNT:face_count"
+}
+
 # Collects a NormalizedRect for each face into a vector. Upon receiving the
 # BATCH_END timestamp, outputs the vector of NormalizedRect at the BATCH_END
 # timestamp.