Calibration Information

Calibration Information may be provided to fluxEngine in order specify additional information about the measurement setup that may influence details of specific algorithms.

  • The calibration information may be set for an instrument device that has been connected. All processing contexts that are created afterwards are

  • The calibration information may be set for a measurement that is being created. The information will be stored if the measurement is saved.

  • If a measurement includes stored calibration information, if a processing context is created to

  • When creating a manual processing context the user may specify calibration information manually.

Creating a new Calibration Information Structure

The following example shows how to create a calibration information structure and how to set specific calibration values:

 1 try {
 2     fluxEngine::CalibrationInfo calibrationInfo;
 4     // Indicate that the pixel resolution of the object
 5     // imaged is 1mm per pixel:
 6     calibrationInfo.setSetting(fluxEngine::CalibrationSettingType::PixelSizeX,
 7                                1.0, "mm");
 8     // Indicate the camera is 30cm away from the object
 9     // being image
10     calibrationInfo.setSetting(fluxEngine::CalibrationSettingType::InstrumentBaseDistance,
11                                30.0, "cm");
12     // Indicate that the instrument is positioned at an
13     // angle of 1.5 degrees
14     calibrationInfo.setSetting(fluxEngine::CalibrationSettingType::InstrumentAngleX,
15                                1.5, "deg");
17     // Specify a white reference material
18     std::vector<double> const whiteRef_lambda{400.0, 500.0, 600.0, 700.0, 800.0, 900.0};
19     std::vector<double> const whiteRef_R{0.99, 0.99, 0.99, 0.99, 0.99, 0.98};
20     calibrationInfo.setWhiteReferenceReflectivity(whiteRef_lambda, whiteRef_R, "nm");
21 } catch (std::exception& e) {
22     std::cerr << "An error occurred: " << e.what() << std::endl;
23     exit(1);
24 }

Using the Calibration Information for Device Processing Contexts

The following example shows how the calibration information that was mentioned beforehand may be used to create device processing contexts:

 1 // From before:
 2 fluxEngine::CalibrationInfo calibrationInfo = ...;
 3 fluxEngine::InstrumentDevice* camera = ...;
 4 fluxEngine::Model model = ...;
 5 fluxEngine::InstrumentParameters parameters = ...;
 6 try {
 7     using fluxEngine::ProcessingContext;
 8     ProcessingContext ctx1 =
 9         ProcessingContext::createInstrumentProcessingContext(camera, model, parameters);
11     camera->setCalibrationInfo(calibrationInfo);
13     ProcessingContext ctx2 =
14         ProcessingContext::createInstrumentProcessingContext(camera, model, parameters);
16     // ctx1 will use the old calibration information
17     // (if any at all), while ctx2 will use the
18     // calibration information stored in calibrationInfo.
19 } catch (std::exception& e) {
20     std::cerr << "An error occurred: " << e.what() << std::endl;
21     exit(1);
22 }


Calibration Information currently has no effect on preview processing contexts (and likely never will). It does have an effect on recording processing contexts though. For example, if a white reference reflectivity curve is specified, and the recording is to take place in reflectances, that curve will be considered when calculating reflectance values.

Also, the fluxEngine::ProcessingContext::HSIRecordingResult structure will contain the calibration information structure that will be valid for the recording if it were to be stored. Important: the calibration information may be different than the supplied calibration information. For example, if software binning is enabled, the raw calibration information that must be supplied to the instrument device by the user must be for the raw pixels of the sensor, while the calibration information stored in the fluxEngine::ProcessingContext::HSIRecordingResult structure will have been adjusted for the binning factor, because a binned pixel will cover a larger part of the object than the unbinned (raw) pixel. There are other ways in which the preprocessing that is performed may have an influence, and fluxEngine ensures that this is handled properly.