# Example Fiducial Square Binary

Demonstration how to detect square binary fiducials. Square binary fiducials encode a pattern in the fiducial's center which can describe up to 4096 unique targets.

Example Code:

Concepts:

• Fiducials
• Pose estimation

Relevant Examples/Tutorials:

Videos

# Example Code

```/**
* Detects square binary fiducials inside an image, writes out there pose, and visualizes a virtual flat cube
* above them in the input image.
*
* @author Peter Abeles
*/
public class ExampleFiducialBinary {
public static void main(String[] args) {

String directory = UtilIO.pathExample("fiducial/binary");

// load the lens distortion parameters and the input image
CameraPinholeBrown param = CalibrationIO.load(new File(directory , "intrinsic.yaml"));
LensDistortionNarrowFOV lensDistortion = new LensDistortionBrown(param);

BufferedImage input = UtilImageIO.loadImage(directory , "image0000.jpg");
//		BufferedImage input = UtilImageIO.loadImage(directory , "image0001.jpg");
//		BufferedImage input = UtilImageIO.loadImage(directory , "image0002.jpg");
GrayF32 original = ConvertBufferedImage.convertFrom(input,true, ImageType.single(GrayF32.class));

// Detect the fiducial
FiducialDetector<GrayF32> detector = FactoryFiducial.squareBinary(
new ConfigFiducialBinary(0.1), ConfigThreshold.local(ThresholdType.LOCAL_MEAN, 21), GrayF32.class);
//				new ConfigFiducialBinary(0.1), ConfigThreshold.fixed(100),GrayF32.class);

detector.setLensDistortion(lensDistortion,param.width,param.height);
detector.detect(original);

// print the results
Graphics2D g2 = input.createGraphics();
Se3_F64 targetToSensor = new Se3_F64();
Point2D_F64 locationPixel = new Point2D_F64();
Polygon2D_F64 bounds = new Polygon2D_F64();
for (int i = 0; i < detector.totalFound(); i++) {
detector.getCenter(i, locationPixel);
detector.getBounds(i, bounds);

g2.setColor(new Color(50,50,255));
g2.setStroke(new BasicStroke(10));
VisualizeShapes.drawPolygon(bounds,true,1.0,g2);

if( detector.hasID() )
System.out.println("Target ID = "+detector.getId(i));
if( detector.hasMessage() )
System.out.println("Message   = "+detector.getMessage(i));
System.out.println("2D Image Location = "+locationPixel);

if( detector.is3D() ) {
detector.getFiducialToCamera(i, targetToSensor);
System.out.println("3D Location:");
System.out.println(targetToSensor);
VisualizeFiducial.drawCube(targetToSensor, param, detector.getWidth(i), 3, g2);
VisualizeFiducial.drawLabelCenter(targetToSensor, param, "" + detector.getId(i), g2);
} else {
VisualizeFiducial.drawLabel(locationPixel, "" + detector.getId(i), g2);
}
}

ShowImages.showWindow(input,"Fiducials",true);
}
}
```