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Calibrate gaze position
=======================
Gaze position calibration is an optional [ArFrame](../../../argaze.md/#argaze.ArFeatures.ArFrame) pipeline step. It processes each new gaze position before any further pipeline steps.
The calibration algorithm can be selected by instantiating a particular [GazePositionCalibrator from GazeAnalysis submodule](../pipeline_modules/gaze_position_calibrators.md) or [from another Python package](module_loading.md).
## Enable ArFrame calibration
Gaze position calibration can be enabled thanks to a dedicated JSON entry.
Here is an extract from the JSON ArFrame configuration file where a [Linear Regression](../../../argaze.md/#argaze.GazeAnalysis.LinearRegression) calibration algorithm is selected with no parameters:
```json
{
"name": "My FullHD screen",
"size": [1920, 1080],
...
"gaze_position_calibrator": {
"LinearRegression": {}
},
...
```
!!! note
When a [GazePositionCalibrator](../../../argaze.md/#argaze.GazeFeatures.GazePositionCalibrator) is instantiated, each gaze position passed to [ArFrame.look](../../../argaze.md/#argaze.ArFeatures.ArFrame.look) method will be transformed before gaze movement identification step.
## Edit calibration parameters
```python
# Assuming the ArFrame is loaded
...
# Start calibration process
ar_frame.gaze_position_calibrator.reset()
# Assuming that expected and observed gaze positions are available
...
# If calibration process started
if ar_frame.gaze_position_calibrator.is_calibrating():
# Store calibration data
ar_frame.gaze_position_calibrator.store(timestamp, observed_gaze_position, expected_gaze_position)
# End calibration process
score = ar_frame.gaze_position_calibrator.calibrate()
```
## Save calibration parameters as JSON file
Calibration parameters can be save as JSON file:
```python
ar_frame.gaze_position_calibrator.to_json('calibration.json')
```
Here is the saved JSON file where calibration parameters are stored:
```json
{
"argaze.GazeAnalysis.LinearRegression": {
"coefficients": [
[
0.901167941442693,
0.0345129853595345
],
[
0.11551395622739168,
0.9315744785596141
]
],
"intercept": [
65.43372920399452,
-52.23141937917768
]
}
}
```
## Load calibration parameters file
Saved calibration parameters can be loaded from JSON ArFrame configuration file:
```json
{
"name": "My FullHD screen",
"size": [1920, 1080],
...
"gaze_position_calibrator": "calibration.json"
...
```
They also can be loaded from Python script:
```python
ar_frame.gaze_position_calibrator.from_json('calibration.json')
```
|
