ScreenBasedCalibration

Provides methods and properties for managing calibrations for screen based eye trackers.

calib = ScreenBasedCalibration(tracker)

Enter Calibration Mode
Leave Calibration Mode
Collect Data
Discard Data
Compute and Apply Calibration
Code Example
See Also
Version

Enter Calibration Mode

Enters the Calibration Mode and the Eye Tracker is made ready for collecting data and calculating new calibrations.

calib.enter_calibration_mode()

Leave Calibration Mode

Leaves the Calibration Mode.

calib.leave_calibration_mode()

Collect Data

Adds data to the temporary calibration buffer for one calibration point. The argument used is the point the calibration user is assumed to be looking at and is given in the Active Display Area Coordinate System.

Parameters: coordinates (x,y) of the calibration point.

calib.collect_data(coordinates)

Discard Data

Removes the data associated with a specific calibration point from the temporary calibration buffer.

Parameters: coordinates (x,y) of the calibration point.

calib.discard_data(coordinates)

Compute and Apply Calibration

Uses the collected data and tries to compute calibration Parameters. If the calculation is successful, the result is applied to the eye tracker. If there is insufficient data to compute a new calibration or if the collected data is not good enough then calibration is failed and will not be applied.

Returns: an instance of the class CalibrationResult

calib.compute_and_apply()

Code Example

%% Calibration Sample
Tobii = EyeTrackingOperations();

eyetracker_address = 'Address of the desired device';
% Example:
% eyetracker_address = 'tet-tcp://172.28.195.1';

eyetracker = Tobii.get_eyetracker(eyetracker_address);

calib = ScreenBasedCalibration(eyetracker);

calib.enter_calibration_mode()

points_to_collect = [[0.1,0.1];[0.1,0.9];[0.5,0.5];[0.9,0.1];[0.9,0.9]];

% When collecting data a point should be presented on the screen in the
% appropriate position.
for i=1:size(points_to_collect,1)
    collect_result = calib.collect_data(points_to_collect(i,:));
    fprintf('Point [%.2f,%.2f] Collect Result: %s\n',points_to_collect(i,:),char(collect_result));
end

calibration_result = calib.compute_and_apply();
fprintf('Calibration Status: %s\n',char(calibration_result.Status));

% After analisyng the calibration result one might want to re-calibrate
% some of the points
points_to_collect = [[0.1,0.1];[0.1,0.9];[0.5,0.5];[0.9,0.1];[0.9,0.9]];

% When collecting data a point should be presented on the screen in the
% appropriate position.

points_to_recalibrate = [[0.1,0.1];[0.1,0.9]];

for i=1:size(points_to_recalibrate,1)
    calib.discard_data(points_to_recalibrate(i,:));
    collect_result = calib.collect_data(points_to_recalibrate(i,:));
    fprintf('Point [%.2f,%.2f] Collect Result: %s\n',points_to_recalibrate(i,:),char(collect_result));
end

calibration_result = calib.compute_and_apply();
fprintf('Calibration Status: %s\n',char(calibration_result.Status));

if calibration_result.Status == CalibrationStatus.Success
        points = calibration_result.CalibrationPoints;

        number_points = size(points,2);

        for i=1:number_points
            plot(points(i).PositionOnDisplayArea(1),points(i).PositionOnDisplayArea(2),'ok','LineWidth',10);
            mapping_size = size(points(i).RightEye,2);
            set(gca, 'YDir', 'reverse');
            axis([-0.2 1.2 -0.2 1.2])
            hold on;
            for j=1:mapping_size
                if points(i).LeftEye(j).Validity == CalibrationEyeValidity.ValidAndUsed
                    plot(points(i).LeftEye(j).PositionOnDisplayArea(1), points(i).LeftEye(j).PositionOnDisplayArea(2),'-xr','LineWidth',3);
                end
                if points(i).RightEye(j).Validity == CalibrationEyeValidity.ValidAndUsed
                    plot(points(i).RightEye(j).PositionOnDisplayArea(1),points(i).RightEye(j).PositionOnDisplayArea(2),'xb','LineWidth',3);
                end
            end

        end
end

calib.leave_calibration_mode()

Version

1.1.0.23