iOS Detection Preferences
Use Detection Preferences to enable and configure facial detection characteristics.
The Enable face detector check box must be selected to enable face recognition.
- Enable face detector: Enables face detection. Note that face detection must be enabled for face recognition to occur.
- Max vertical resolution: Specifies the maximum supported vertical resolution.
- Min searched face size: Defines the minimum face size that can be detected. A searched size of 80, for example, can still manage to detect faces as small as 60x60, but with lower certainty. Lowering this number enables SAFR to detect much smaller faces but also greatly increases CPU usage.
Note: This setting does not impact face recognition accuracy.
- Min required face size: Defines the minimum required size for a face to be detected. Any face smaller than the height or width is ignored.
- Generate recognizer hint: Optimizes facial recognition. It should be turned on for most cases. If it is turned off, recognition accuracy may be reduced if detection is performed at very low resolutions.
- Detection service: Specifies which face detection service will be used.
- SAFR: The standard facial detection service that SAFR uses.
- SAFR Retina: A high sensitivity facial detection service which has a lower latency and whose performance doesn't degrade when multiple faces are being analyzed simultaneously. The SAFR Retina service consumes many more GPU resourcs than the SAFR service.
- CoreImage: A face detection service native to Apple. Its performance is comparable to SAFR's, but it's slightly less accurate.
- Vision: A face detection service native to Apple that's faster but much less accurate.
- Detection thresholds: Allows you to configure the detection thresholds.
- Enable Custom Thresholds: Allows you to customize the detection threshold. When this setting is checked, you can click on the Configure button to do the customization.
- Initial Candidate Threshold: Initial face candidate threshold that is used during face detection.
- Middle Candidate Threshold: Middle face candidate threshold that is used during face detection.
- Final Candidate Threshold: Final face candidate threshold that is used during face detection.
- Detection Sensitivity Threshold: The lower this value is, the more lenient the facial detection service will be when attempting to recognize a face, which can result in additional false positives.
- Validation service: Requires a mobile device with a TrueDepth camera. When set to Real Face, this setting uses the device's TrueDepth camera to do a liveness test on any faces in view of the camera. If the faces pass the test, then they are indeed real faces. Any faces that fail the test are probably spoofs. If this setting is set to None, or if the device doesn't have a TrueDepth camera, then no liveness test is performed.
The Enable badge detector check box must be selected to enable badge detection. Badges are visual representations of users that are quicker and easier to detect than faces. Compared to faces, they are easier to detect and recognize when rotated and when used in low light conditions.
- Max vertical resolution: Specifies the maximum supported vertical resolution.
- Min searched badge size: Defines the minimum badge size that can be detected. Lowering this value enables SAFR to detect very small badges (down to 15x15 pixels) at the cost of increasing the CPU usage. Conversely, increasing this value reduces CPU usage but requires larger badges for successful detection.
- Min required badge size: Use this setting to require a minimum badge size in pixels. Any badge smaller than this value in either height or width is ignored. This setting is mainly used when badge detection is only expected to occur when the badges are close to the camera. (When cameras are close to the camera, the badge sizes are guaranteed to be larger.) If this value is set too small, SAFR could create many detection events for badges that are far from the camera and therefore not of interest.
- Consecutive confirmations required: This setting adds consecutive confirmations to the SAFR detection to create more reliable detections. Increase this setting for more reliable but slower badge detection. Decrease it for faster but slightly less reliable detection.
- Detection service: Specifies which badge detection method will be used. Depending on the capabilities of your cameras, lighting conditions, and other variables, certain options may work better with your environment than others.
You can choose from the following options:
- apriltags: Basic badge detection.
- rhinotagsLite: The fastest badge detector, but it has a lower tolerance for motion blur. It requires cameras with a fast shutter speed.
- rhinotagsTeam: Faster badge detector, but it has little resilience to motion blur.
- rhinotagsFlex: Fast badge detector with moderate resilience to motion blur.
- rhinotagsFull: Badge detector with robust handling under various conditions and a strong resilience to motion blur.
rhinotagsFull is the recommended option.
A full set of badge images supported by SAFR is available at https://github.com/anqixu/apriltag/tree/master/tag36h11.
- It is recommended these images be re-sized to at least 2" x 2" size using the nearest neighbor algorithm (to maintain sharp edges) before use with SAFR.
- Although a single badge of displayed format can express only 587 different IDs, multiple badges can be combined to increase the number of expressible IDs into the billions. For example, using 6 badges providesover 827 billion expressible IDs.