Image tracking apparatus

1. An image tracking apparatus, which tracks a subject in a moving image in which the subject is captured, comprising:

an image acquisition device that acquires image data indicating the moving image;

a first detector that detects a first area of at least one subject in acquired image data to track the first area in the moving image;

a second detector that detects a second area of at least one subject in the image data to track the second area in the moving image; and

a controller that tracks the subject by switching between a tracking result of the first area by the first detector and a tracking result of the second area by the second detector,

wherein the first detector and the second detector operate independently of each other whereby the first detector detects the first area independent of the second detector detecting the second area, and the second detector detects the second area independent of the first detector detecting the first area, and

wherein the controller

tracks the subject using the tracking result of the first detector when the first area is tracked by the first detector, and

tracks the subject using the tracking result of the second detector when the first area is not tracked by the first detector and the second area is tracked by the second detector.

2. The image tracking apparatus according to claim 1 , wherein

in response to loss of the first area by the first detector, the controller determines whether the first area and the second area indicate an identical subject based on a positional relation between the first area and the second area, and

upon determining that the first and second areas indicate the identical subject, the controller switches from the tracking result of the first detector to the tracking result of the second detector.

3. The image tracking apparatus according to claim 2 , wherein

after switching to the tracking result of the second detector, the controller switches from the tracking result of the second detector to the tracking result of the first detector upon tracking the first area by the first detector.

4. The image tracking apparatus according to claim 1 , wherein

an operation period with which the first detector detects the first area of the subject is shorter than an operation period with which the second detector detects the second area of the subject.

5. The image tracking apparatus according to claim 1 , wherein

the first detector detects a face area corresponding to a face of the subject to track the face area in the moving image, and

the second detector detects a head area corresponding to a head including a face of the subject to track the head area in the moving image.

6. The image tracking apparatus according to claim 5 , wherein upon switching from the tracking result of the first detector to the tracking result of the second detector, the controller tracks the subject by using the tracking result of the second detector according to positional relation that the face area is included in the head area.

7. The image tracking apparatus according to claim 5 , wherein upon switching from the tracking result of the second detector to the tracking result of the first detector, the controller tracks the subject by using the tracking result of the first detector according to positional relation that the face area is included in the head area.

8. The image tracking apparatus according to claim 5 , wherein

the first detector tracks each of face areas of a plurality of subjects, and/or the second detector tracks each of head areas of the plurality of subjects, and

the controller tracks a main subject and one or more other subjects in the plurality of subjects respectively, based on tracking results of the first detector and tracking results of the second detector.

9. The image tracking apparatus according to claim 5 , further comprising

an operation interface that inputs a user operation to set a main subject,

wherein

the controller manages main subject information based on the tracking results of the first and second detectors to track the main subject in the moving image, the main subject information identifying the main subject in the image data, and

in response to input of a user operation to change the main subject in a state where a plurality of areas corresponding to the plurality of subjects are tracked by the first and second detectors,

the controller updates the main subject information to replace information identifying the main subject before changed with information identifying the main subject after changed, based on the tracking results of the first or second detector at the input of the user operation.

10. The image tracking apparatus according to claim 5 , wherein

the tracking result of the first detector includes a position and a size of the face area in the image data, and the tracking result of the second detector includes a position and a size of the head area in the image data.

11. An image tracking apparatus, which tracks a subject in a moving image in which the subject is captured, comprising:

an image acquisition device that acquires image data indicating the moving image;

a plurality of detectors each of which detects an area of at least one subject in acquired image data to track the detected area in the moving image; and

a controller that tracks the subject by switching among tracking results of the areas of the subject obtained by each of the plurality of detectors,

wherein

the plurality of detectors include at least a first detector that detects a first area as an area of the subject and a second detector that detects a second area as an area of the subject, and

first operation period which is a cyclic period for the first detector to execute detection of the first area is shorter than second operation period which is a cyclic period for the second detector to execute detection of the second area, and

wherein the controller

tracks the subject using a tracking result of the first detector when the first area is tracked by the first detector,

tracks the subject using a tracking result of the second detector when the first area is not tracked by the first detector and the second area is tracked by the second detector, and

wherein after switching to the tracking result of the second detector, the controller switches from the tracking result of the second detector operating in the second operation period to the tracking result of the first detector upon tracking the first area by the first detector operating in the first operation period.

12. The image tracking apparatus according to claim 11 , wherein

the plurality of detectors include a third detector that detects a third area different from the first and second areas as an area of the subject, and

an operation period with which the third detector detects the third area is longer than the operation period with which the second detector detects the second area, and

wherein the controller tracks the subject using a tracking result of the third detector when the second area is not tracked by the second detector and the third area is tracked by the third detector.

13. The image tracking apparatus according to claim 12 , wherein

the controller

switches from the tracking result of the first detector to the tracking result of the second detector upon loss of the first area by the first detector,

switches from the tracking result of the second detector to the tracking result of the third detector upon loss of the second area by the second detector, and

wherein after switching to the tracking result of the third detector, the controller switches from the tracking result of the third detector to the tracking result of the first detector upon tracking the first area by the first detector.

14. An image tracking apparatus, which tracks a subject in a moving image in which the subject is captured, comprising:

an image acquisition device that acquires image data indicating the moving image;

a first detector that detects a first area of at least one subject in acquired image data to track the first area in the moving image;

a second detector that detects a second area of at least one subject in the image data to track the second area in the moving image; and

a controller that tracks the subject by switching between a tracking result of the first area by the first detector and a tracking result of the second area by the second detector,

wherein an operation period which is a cyclic period for the first detector to execute detection of the first area and an operation period which is a cyclic period for the second detector to execute detection of the second area are the same, and

wherein the controller

tracks the subject using a tracking result of the first detector when the first area is tracked by the first detector,

tracks the subject using a tracking result of the second detector when the first area is not tracked by the first detector and the second area is tracked by the second detector, and

wherein after switching to the tracking result of the second detector, the controller continues tracking the subject using the tracking result of the second detector when the first area is tracked by the first detector with the second detector tracking the second area.

15. The image tracking apparatus according to claim 14 , wherein

when the first area is tracked by the first detector after switching to the tracking result of the second detector,

the controller

does not switch from the tracking result of the second detector to the tracking result of the first detector upon tracking the second area by the second detector, and

switches from the tracking result of the second detector to the tracking result of the first detector upon lost of the second area by the second detector.