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 the 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 with 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 { "argaze.ArFeatures.ArFrame": { "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') ```