Add a face to a specified face list, up to 1,000 faces. <br /> To deal with an image contains multiple faces, input face can be specified as an image with a targetFace rectangle. It returns a persistedFaceId representing the added face. No image will be stored. Only the extracted face feature will be stored on server until FaceList - Delete Face or FaceList - Delete is called. <br /> Note persistedFaceId is different from faceId generated by Face - Detect.

• Higher face image quality means better detection and recognition precision. Please consider high-quality faces: frontal, clear, and face size is 200x200 pixels (100 pixels between eyes) or bigger.
• JPEG, PNG, GIF (the first frame), and BMP format are supported. The allowed image file size is from 1KB to 6MB.
• "targetFace" rectangle should contain one face. Zero or multiple faces will be regarded as an error. If the provided "targetFace" rectangle is not returned from Face - Detect, there’s no guarantee to detect and add the face successfully.
• Out of detectable face size (36x36 - 4096x4096 pixels), large head-pose, or large occlusions will cause failures.
• Adding/deleting faces to/from a same face list are processed sequentially and to/from different face lists are in parallel.
• The minimum detectable face size is 36x36 pixels in an image no larger than 1920x1080 pixels. Images with dimensions higher than 1920x1080 pixels will need a proportionally larger minimum face size.
• Different 'detectionModel' values can be provided. To use and compare different detection models, please refer to How to specify a detection model.