Example Calibrate Planar Mono

Monocular Camera Calibration with Planar Targets

• 

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

Calibrating a monocular (single) camera is the process of learning its intrinsic camera parameters and removing lens distortion. This example demonstrates how to use multiple pictures of a planar calibration target. 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: ExampleBinaryImage.java

Calibration Tutorial: Tutorial Here

Concepts:

• Camera calibration
• Lens distortion
• Intrinsic parameters

Relevant Applets:

• Binary Operations
• Binary Segmentation

Related Examples:

• Stereo Camera Calibration
• Removing Lens Distortion

Example Code

/**
 * <p>
 * Example of how to calibrate a single (monocular) camera using a planar calibration grid.  Two types of calibration
 * targets can be processed by BoofCV, square grids and chessboard.  Square grid is composed of a set of square
 * grids and chessboard is a classic chessboard pattern.  In general better quality results have been found using
 * the chessboard pattern, but parameter tuning is required to achieve optimal performance.
 * </p>
 *
 * <p>
 * All the image processing and calibration is taken care of inside of {@link CalibrateMonoPlanar}.  The code below
 * images of calibration targets are loaded and pass in as inputs and the found calibration is saved to an XML file.
 * See in code comments for tuning and implementation issues.
 * </p>
 *
 * @see ExampleCalibrateStereoPlanar
 *
 * @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;

	// Most computer images are in a left handed coordinate system.  This can cause problems when algorithms
	// that assume a right handed coordinate system are used later on.  To address this issue the image coordinate
	// system is changed to a right handed one if true is passed in for the second parameter.
	boolean isLeftHanded;

	/**
	 * Images from Zhang's website.  Square grid pattern.
	 */
	private void setupZhang99() {
		// Use the wrapper below for square grid targets.
		detector = new WrapPlanarGridTarget(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
		isLeftHanded = true;
	}

	/**
	 * 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 = new WrapPlanarChessTarget(3,4,6);

		// 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
		isLeftHanded = true;
	}

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

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

		// 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);
				calibrationAlg.addImage(image);
			}
		}
		// 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();
	}
}