Updated iOS gesture recognizer results to initialize hand gestures with a default index

mediapipe/tasks/ios/components/containers/utils/sources/MPPCategory+Helpers.h

@@ -19,8 +19,30 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface MPPCategory (Helpers)
 
+/**
+ * Creates an `MPPCategory` with the given MediaPipe `Classification` proto.
+ *
+ * @param classificationProto A MediaPipe `Classification` proto.
+ * @return  An `MPPCategory` object that with the given MediaPipe `Classification` proto.
+ */
 + (MPPCategory *)categoryWithProto:(const ::mediapipe::Classification &)classificationProto;
 
+/**
+ * Creates an `MPPCategory` with the given MediaPipe `Classification` proto and the given category
+ * index. The resulting `MPPCategory` is created with the given category index instead of the
+ * category index specified in the `Classification` proto. This method is useful for tasks like
+ * gesture recognizer which always returns a default index for the recognized gestures.
+ *
+ * @param classificationProto A MediaPipe `Classification` proto.
+ * @param index The index to be used for creating the `MPPCategory` instead of the category index
+ * specified in the `Classification` proto.
+ *
+ * @return  An `MPPGestureRecognizerResult` object that contains the hand gesture recognition
+ * results.
+ */
++ (MPPCategory *)categoryWithProto:(const ::mediapipe::Classification &)classificationProto
+                             index:(NSInteger)index;
+
 @end
 
 NS_ASSUME_NONNULL_END

mediapipe/tasks/ios/components/containers/utils/sources/MPPCategory+Helpers.mm

@@ -21,7 +21,8 @@ using ClassificationProto = ::mediapipe::Classification;
 
 @implementation MPPCategory (Helpers)
 
-+ (MPPCategory *)categoryWithProto:(const ClassificationProto &)classificationProto {
++ (MPPCategory *)categoryWithProto:(const ClassificationProto &)classificationProto
+                             index:(NSInteger)index {
   NSString *categoryName;
   NSString *displayName;
 
@@ -33,10 +34,14 @@ using ClassificationProto = ::mediapipe::Classification;
     displayName = [NSString stringWithCppString:classificationProto.display_name()];
   }
 
-  return [[MPPCategory alloc] initWithIndex:classificationProto.index()
+  return [[MPPCategory alloc] initWithIndex:index
                                       score:classificationProto.score()
                                categoryName:categoryName
                                 displayName:displayName];
 }
 
++ (MPPCategory *)categoryWithProto:(const ClassificationProto &)classificationProto {
+  return [MPPCategory categoryWithProto:classificationProto index:classificationProto.index()];
+}
+
 @end

mediapipe/tasks/ios/vision/gesture_recognizer/utils/sources/MPPGestureRecognizerResult+Helpers.h

@@ -14,6 +14,8 @@
 
 #import "mediapipe/tasks/ios/vision/gesture_recognizer/sources/MPPGestureRecognizerResult.h"
 
+#include "mediapipe/framework/formats/classification.pb.h"
+#include "mediapipe/framework/formats/landmark.pb.h"
 #include "mediapipe/framework/packet.h"
 
 NS_ASSUME_NONNULL_BEGIN
@@ -23,14 +25,14 @@ static const int kMicroSecondsPerMilliSecond = 1000;
 @interface MPPGestureRecognizerResult (Helpers)
 
 /**
- * Creates an `MPPGestureRecognizerResult` from hand gestures, handedness, hand landmarks and world
+ * Creates an `MPPGestureRecognizerResult` from  hand gestures, handedness, hand landmarks and world
  * landmarks packets.
  *
- * @param handGesturesPacket a MediaPipe packet wrapping a`std::vector<ClassificationListProto>`.
+ * @param handGesturesPacket A MediaPipe packet wrapping a`std::vector<ClassificationListProto>`.
- * @param handednessPacket a MediaPipe packet wrapping a`std::vector<ClassificationListProto>`.
+ * @param handednessPacket A MediaPipe packet wrapping a`std::vector<ClassificationListProto>`.
- * @param handLandmarksPacket a MediaPipe packet wrapping
+ * @param handLandmarksPacket A MediaPipe packet wrapping
  * a`std::vector<NormalizedlandmarkListProto>`.
- * @param handLandmarksPacket a MediaPipe packet wrapping a`std::vector<LandmarkListProto>`.
+ * @param worldLandmarksPacket A MediaPipe packet wrapping a`std::vector<LandmarkListProto>`.
  *
  * @return  An `MPPGestureRecognizerResult` object that contains the hand gesture recognition
  * results.

mediapipe/tasks/ios/vision/gesture_recognizer/utils/sources/MPPGestureRecognizerResult+Helpers.mm

@@ -21,6 +21,8 @@
 #include "mediapipe/framework/formats/landmark.pb.h"
 #include "mediapipe/framework/packet.h"
 
+static const NSInteger kDefaultGestureIndex = -1;
+
 namespace {
 using ClassificationListProto = ::mediapipe::ClassificationList;
 using LandmarkListProto = ::mediapipe::LandmarkList;
@@ -30,6 +32,15 @@ using ::mediapipe::Packet;
 
 @implementation MPPGestureRecognizerResult (Helpers)
 
++ (MPPGestureRecognizerResult *)emptyGestureRecognizerResultWithTimestampInMilliseconds:
+    (NSInteger)timestampInMilliseconds {
+  return [[MPPGestureRecognizerResult alloc] initWithGestures:@[]
+                                                   handedness:@[]
+                                                    landmarks:@[]
+                                               worldLandmarks:@[]
+                                      timestampInMilliseconds:timestampInMilliseconds];
+}
+
 + (MPPGestureRecognizerResult *)
     gestureRecognizerResultWithHandGesturesPacket:(const Packet &)handGesturesPacket
                                  handednessPacket:(const Packet &)handednessPacket
@@ -39,18 +50,16 @@ using ::mediapipe::Packet;
       (NSInteger)(handGesturesPacket.Timestamp().Value() / kMicroSecondsPerMilliSecond);
 
   if (handGesturesPacket.IsEmpty()) {
-    return [[MPPGestureRecognizerResult alloc] initWithGestures:@[]
+    return [MPPGestureRecognizerResult
-                                                     handedness:@[]
+        emptyGestureRecognizerResultWithTimestampInMilliseconds:timestampInMilliseconds];
-                                                      landmarks:@[]
-                                                 worldLandmarks:@[]
-                                        timestampInMilliseconds:timestampInMilliseconds];
   }
 
   if (!handGesturesPacket.ValidateAsType<std::vector<ClassificationListProto>>().ok() ||
       !handednessPacket.ValidateAsType<std::vector<ClassificationListProto>>().ok() ||
       !handLandmarksPacket.ValidateAsType<std::vector<NormalizedLandmarkListProto>>().ok() ||
       !worldLandmarksPacket.ValidateAsType<std::vector<LandmarkListProto>>().ok()) {
-    return nil;
+    return [MPPGestureRecognizerResult
+        emptyGestureRecognizerResultWithTimestampInMilliseconds:timestampInMilliseconds];
   }
 
   const std::vector<ClassificationListProto> &handGesturesClassificationListProtos =
@@ -62,7 +71,7 @@ using ::mediapipe::Packet;
     NSMutableArray<MPPCategory *> *gestures = [NSMutableArray
         arrayWithCapacity:(NSUInteger)classificationListProto.classification().size()];
     for (const auto &classificationProto : classificationListProto.classification()) {
-      MPPCategory *category = [MPPCategory categoryWithProto:classificationProto];
+      MPPCategory *category = [MPPCategory categoryWithProto:classificationProto index:kDefaultGestureIndex];
       [gestures addObject:category];
     }
     [multiHandGestures addObject:gestures];