Example Calibrate Planar Mono

• 

  Left uncalibrated. Right calibrated with lens distortion removed. Numbers are super imposed on the image to show calibration points.

This example demonstrates how to use a high level calibration class that automatically detects calibration targets as viewed from a single (monocular) camera in a set of images. After processing the images the intrinsic camera parameters and lens distortion are saved to an XML file. Both the square grid and chessboard patterns are supported by this example. For a full description of the calibration process and instruction on how to do it yourself see the tutorial linked to below.

Example File: ExampleCalibrateMonocularPlanar.java

Calibration Tutorial: Wikipage

Concepts:

• Camera calibration
• Lens distortion
• Intrinsic parameters

Relevant Applets:

• Monocular Calibration
• Removing Lens Distortion

Related Examples:

• Stereo Camera Calibration
• Removing Lens Distortion

Example Code

/**
 * Example of how to calibrate a single (monocular) camera using a high level interface that processes images of planar
 * calibration targets.  The entire calibration target must be observable in the image and for best results images
 * should be in focus and not blurred.  For a lower level example of camera calibration which processes a set of
 * observed calibration points see {@link ExampleCalibrateMonocularPlanar}.
 *
 * After processing both intrinsic camera parameters and lens distortion are estimated.  Square grid and chessboard
 * targets are demonstrated by this example. See calibration tutorial for a discussion of different target types
 * and how to collect good calibration images.
 *
 * All the image processing and calibration is taken care of inside of {@link CalibrateMonoPlanar}.  The code below
 * loads calibration images as inputs, calibrates, and saves results to an XML file.  See in code comments for tuning
 * and implementation issues.
 *
 * @see CalibrateMonoPlanar
 *
 * @author Peter Abeles
 */
public class ExampleCalibrateMonocularPlanar {

	// Detects the target and calibration point inside the target
	PlanarCalibrationDetector detector;

	// Description of the target's physical dimension
	PlanarCalibrationTarget target;

	// List of calibration images
	List<String> images;

	// Many 3D operations assumed a right handed coordinate system with +Z pointing out of the image.
	// If the image coordinate system is left handed then the y-axis needs to be flipped to meet
	// that requirement.  Most of the time this is false.
	boolean flipY;

	/**
	 * Images from Zhang's website.  Square grid pattern.
	 */
	private void setupZhang99() {
		// Use the wrapper below for square grid targets.
		detector = FactoryPlanarCalibrationTarget.detectorSquareGrid(new ConfigSquareGrid(8, 8));

		// physical description
		target = FactoryPlanarCalibrationTarget.gridSquare(8, 8, 0.5, 7.0 / 18.0);

		// load image list
		String directory = "../data/evaluation/calibration/mono/PULNiX_CCD_6mm_Zhang";
		images = BoofMiscOps.directoryList(directory,"CalibIm");

		// standard image format
		flipY = false;
	}

	/**
	 * Images collected from a Bumblee Bee stereo camera.  Large amounts of radial distortion. Chessboard pattern.
	 */
	private void setupBumbleBee() {
		// Use the wrapper below for chessboard targets.  The last parameter adjusts the size of the corner detection
		// region.  TUNE THIS PARAMETER FOR OPTIMAL ACCURACY!
		detector = FactoryPlanarCalibrationTarget.detectorChessboard(new ConfigChessboard(3,4));

		// physical description
		target = FactoryPlanarCalibrationTarget.gridChess(3, 4, 30);

		// load image list
		String directory = "../data/evaluation/calibration/stereo/Bumblebee2_Chess";
		images = BoofMiscOps.directoryList(directory,"left");

		// standard image format
		flipY = false;
	}

	/**
	 * Process calibration images, compute intrinsic parameters, save to a file
	 */
	public void process() {

		// Declare and setup the calibration algorithm
		CalibrateMonoPlanar calibrationAlg = new CalibrateMonoPlanar(detector, flipY);

		// tell it type type of target and which parameters to estimate
		calibrationAlg.configure(target, true, 2);

		for( String n : images ) {
			BufferedImage input = UtilImageIO.loadImage(n);
			if( n != null ) {
				ImageFloat32 image = ConvertBufferedImage.convertFrom(input,(ImageFloat32)null);
				if( !calibrationAlg.addImage(image) )
					System.err.println("Failed to detect target in "+n);
			}
		}
		// process and compute intrinsic parameters
		IntrinsicParameters intrinsic = calibrationAlg.process();

		// save results to a file and print out
		BoofMiscOps.saveXML(intrinsic, "intrinsic.xml");

		calibrationAlg.printStatistics();
		System.out.println();
		System.out.println("--- Intrinsic Parameters ---");
		System.out.println();
		intrinsic.print();
	}


	public static void main( String args[] ) {
		ExampleCalibrateMonocularPlanar alg = new ExampleCalibrateMonocularPlanar();

		// which target should it process
//		alg.setupZhang99();
		alg.setupBumbleBee();

		// compute and save results
		alg.process();
	}
}