Guiding the person into position
What the widget shows before the capture starts, what each cue means, and what your code receives at the same moment.
A measurement only works if the face sits correctly in the frame, at the right distance, with the upper chest visible. Rather than say it once and hope, Saphere Scan follows the face before the capture and shows, continuously, whether it sits correctly between two guides.
The guidance is shown, not written: it has to work the same way in ten languages and in both reading directions. And it says what to do, not what is wrong.
Conditions for a good measurement explains why the position matters in the first place.
| What the person sees | What it means | What to do |
|---|---|---|
| Arrows pointing down at the upper guide | The face is above the usable area | Move down |
| Arrows pointing up at the lower guide | The face is below the usable area | Move up |
| The frame closing in on itself | The face is bigger than the space between the guides | Move back |
| No marker at all | The position is accepted | Hold still |
Two things about this guidance are worth knowing before you build around it.
The guidance and the accept-or-refuse decision are read from the same rule. Guidance can therefore never appear while the position is accepted, nor be missing while it is refused.
“Move back” is checked first. A face taller than the usable area will not fit by moving in any direction, so telling the person to move up or down would be advice that cannot work.
Your code receives the same information as the screen, through the placement:guidance event: "up", "down", "back", or nothing once the position is accepted. It fires only when the instruction changes, never on every image. See Events.