Example Fit Ellipse

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Fitting ellipses to 2D objects found in images is a common task in industrial and scientific settings. In this example, binary blobs are found inside an image of particles and the best fit ellipses found. In a real application the next step could be to analyze the size distribution of the found ellipses to characterize the particles.

Example Code:

Concepts:

  • Object contours/edges
  • Best fit shape

Relevant Examples:

Example Code

/**
 * Demonstration which fits ellipses to object contours in a binary image.
 *
 * @author Peter Abeles
 */
public class ExampleFitEllipse {

	public static void main( String args[] ) {
		// load and convert the image into a usable format
		BufferedImage image = UtilImageIO.loadImage(UtilIO.pathExample("particles01.jpg"));
		GrayF32 input = ConvertBufferedImage.convertFromSingle(image, null, GrayF32.class);

		GrayU8 binary = new GrayU8(input.width,input.height);

		// the mean pixel value is often a reasonable threshold when creating a binary image
		double mean = ImageStatistics.mean(input);

		// create a binary image by thresholding
		ThresholdImageOps.threshold(input, binary, (float) mean, true);

		// reduce noise with some filtering
		GrayU8 filtered = BinaryImageOps.erode8(binary, 1, null);
		filtered = BinaryImageOps.dilate8(filtered, 1, null);

		// Find the contour around the shapes
		List<Contour> contours = BinaryImageOps.contour(filtered, ConnectRule.EIGHT,null);

		// Fit an ellipse to each external contour and draw the results
		Graphics2D g2 = image.createGraphics();
		g2.setStroke(new BasicStroke(3));
		g2.setColor(Color.RED);

		for( Contour c : contours ) {
			FitData<EllipseRotated_F64> ellipse = ShapeFittingOps.fitEllipse_I32(c.external,0,false,null);
			VisualizeShapes.drawEllipse(ellipse.shape, g2);
		}

//		ShowImages.showWindow(VisualizeBinaryData.renderBinary(filtered, false, null),"Binary",true);
		ShowImages.showWindow(image,"Ellipses",true);
	}
}