Internal change

PiperOrigin-RevId: 499283559

mediapipe/tasks/web/vision/gesture_recognizer/gesture_recognizer.ts

@@ -263,6 +263,15 @@ export class GestureRecognizer extends
         NORM_RECT_STREAM, timestamp);
     this.finishProcessing();
 
+    if (this.gestures.length === 0) {
+      // If no gestures are detected in the image, just return an empty list
+      return {
+        gestures: [],
+        landmarks: [],
+        worldLandmarks: [],
+        handednesses: [],
+      };
+    } else {
       return {
         gestures: this.gestures,
         landmarks: this.landmarks,
@@ -270,6 +279,7 @@ export class GestureRecognizer extends
         handednesses: this.handednesses
       };
     }
+  }
 
   /** Sets the default values for the graph. */
   private initDefaults(): void {
@@ -283,15 +293,19 @@ export class GestureRecognizer extends
   }
 
   /** Converts the proto data to a Category[][] structure. */
-  private toJsCategories(data: Uint8Array[]): Category[][] {
+  private toJsCategories(data: Uint8Array[], populateIndex = true):
+      Category[][] {
     const result: Category[][] = [];
     for (const binaryProto of data) {
       const inputList = ClassificationList.deserializeBinary(binaryProto);
       const outputList: Category[] = [];
       for (const classification of inputList.getClassificationList()) {
+        const index = populateIndex && classification.hasIndex() ?
+            classification.getIndex()! :
+            DEFAULT_CATEGORY_INDEX;
         outputList.push({
           score: classification.getScore() ?? 0,
-          index: classification.getIndex() ?? DEFAULT_CATEGORY_INDEX,
+          index,
           categoryName: classification.getLabel() ?? '',
           displayName: classification.getDisplayName() ?? '',
         });
@@ -375,7 +389,10 @@ export class GestureRecognizer extends
         });
     this.graphRunner.attachProtoVectorListener(
         HAND_GESTURES_STREAM, binaryProto => {
-          this.gestures.push(...this.toJsCategories(binaryProto));
+          // Gesture index is not used, because the final gesture result comes
+          // from multiple classifiers.
+          this.gestures.push(
+              ...this.toJsCategories(binaryProto, /* populateIndex= */ false));
         });
     this.graphRunner.attachProtoVectorListener(
         HANDEDNESS_STREAM, binaryProto => {

mediapipe/tasks/web/vision/gesture_recognizer/gesture_recognizer_result.d.ts

@@ -17,6 +17,8 @@
 import {Category} from '../../../../tasks/web/components/containers/category';
 import {Landmark, NormalizedLandmark} from '../../../../tasks/web/components/containers/landmark';
 
+export {Category, Landmark, NormalizedLandmark};
+
 /**
  * Represents the gesture recognition results generated by `GestureRecognizer`.
  */
@@ -30,6 +32,10 @@ export declare interface GestureRecognizerResult {
   /** Handedness of detected hands. */
   handednesses: Category[][];
 
-  /** Recognized hand gestures of detected hands */
+  /**
+   * Recognized hand gestures of detected hands. Note that the index of the
+   * gesture is always -1, because the raw indices from multiple gesture
+   * classifiers cannot consolidate to a meaningful index.
+   */
   gestures: Category[][];
 }

mediapipe/tasks/web/vision/gesture_recognizer/gesture_recognizer_test.ts

@@ -272,7 +272,7 @@ describe('GestureRecognizer', () => {
     expect(gestures).toEqual({
       'gestures': [[{
         'score': 0.2,
-        'index': 2,
+        'index': -1,
         'categoryName': 'gesture_label',
         'displayName': 'gesture_display_name'
       }]],
@@ -305,4 +305,25 @@ describe('GestureRecognizer', () => {
     // gestures.
     expect(gestures2).toEqual(gestures1);
   });
+
+  it('returns empty results when no gestures are detected', async () => {
+    // Pass the test data to our listener
+    gestureRecognizer.fakeWasmModule._waitUntilIdle.and.callFake(() => {
+      verifyListenersRegistered(gestureRecognizer);
+      gestureRecognizer.listeners.get('hand_landmarks')!(createLandmarks());
+      gestureRecognizer.listeners.get('world_hand_landmarks')!
+          (createWorldLandmarks());
+      gestureRecognizer.listeners.get('handedness')!(createHandednesses());
+      gestureRecognizer.listeners.get('hand_gestures')!([]);
+    });
+
+    // Invoke the gesture recognizer
+    const gestures = gestureRecognizer.recognize({} as HTMLImageElement);
+    expect(gestures).toEqual({
+      'gestures': [],
+      'landmarks': [],
+      'worldLandmarks': [],
+      'handednesses': []
+    });
+  });
 });