Image Input Guidelines
This document summarizes the recommended conditions for input images that allow Liveness Detection (anti-spoofing) to achieve the highest possible accuracy. Images that do not meet these conditions may result in reduced detection accuracy, or the face may not be detected and a 400 invalid_image response may be returned.
Supported Formats
| Item | Requirement |
|---|---|
| File format | jpeg / png |
| Maximum size | 10 MB |
| Image type | A color image captured with a visible-light camera. Infrared (IR) sensor images are not supported. |
Image and Face Size
| Item | Recommendation |
|---|---|
| Frame size | VGA (640×480) or larger |
| Face width | At least 80 px |
Capture the image so that the width of the detected face region is at least 80 px. If the face appears too small, it may not be detected. Increasing the frame size allows you to keep the face region large enough even when capturing from a greater distance.
Brightness
- We recommend an average luminance value of 50.0 or higher for the face region (8-bit, 256 levels).
- Avoid backlighting and dark environments, and capture the image where the entire face is evenly lit.
Face Orientation (Detectable Angle of View)
- We recommend keeping the face within approximately ±30° both vertically and horizontally relative to the frontal position.
- There is individual variation depending on factors such as face shape.
- A profile view, a heavily tilted face, or an extreme downward or upward gaze may not be detected.
Capture Distance
- We recommend a distance of approximately 30 cm to 1 m from the camera to the face.
- Increasing the resolution of the input image allows capture from a greater distance as well (be sure to maintain a face width of at least 80 px).
Recommended Specifications When Capturing Directly with a Camera (Reference)
For a configuration in which the End User captures an image with a camera before liveness detection, we recommend the following on the camera side.
| Item | Recommendation |
|---|---|
| Camera resolution | VGA (640×480) or larger (720p / 1080p, etc. are also acceptable) |
| Capture distance | Approximately 30 cm to 1 m |
| Field of view | Approximately 50° to 110° |
| Lens | Fixed-focus lens recommended |
Checklist
Before sending a detection request, verify that the input image meets the following.
If errors persist, please also refer to the FAQ / Troubleshooting.