This project uses fast radial symmetry (FRS) to detect seed points for convex objects, and assigns boundary pixels to seed-points using distance and gradient metrics. For each detected object (defined by each detected seed-point), an ellipse is fitted using the assigned edge pixels. This builds heavily on Segmentation of Overlapping Elliptical Objects in Silhouette Images by Zafari et al. The following flowchart roughly describes the process:
The entire pipeline can be broken down in to the following major steps:
Description of all major functions:
| Function | Description | Parameters | Page on Thesis |
|---|---|---|---|
| Main | Used to execute the code | Image name and path | N/A |
| MainCode | Called by Main during each iteration | Image name, path, range of radii, resize factor | N/A |
| frst2d | Fast Radial Symmetry algorithm | Image, radii range, alpha (constant = 2), stdFactor (constant = 0.1) | 15 |
| dist2points | Calculates Euclidean distance between 2 points | Coordinates of the 2 points | N/A |
| div | Calculates divergence factor for edge-to-seed-point association | Image, list of seed-points, list of edge-points | 19 |
| angle2points1 | Calculates angle between 2 points (between 0 and 2*pi) | Coordinates of the 2 points | N/A |
| angle2points | Calculates angle between 2 points (between -pi and pi) | Coordinates of the 2 points | N/A |
| preprocessing | Binarizes an image | Threshold factor | 26 |
| EllipseDirectFit | Fits an ellipse into the given data points | List of data points | 22 |
| drawarc | Draws a circular arc between 2 points using their linked seed-point | Association matrix E, the 2 points for drawing arc | 21 |
| drawellipse | Calculates standard ellipse parameters from equation, and draws ellipse between 2 points | Association matrix E, the 2 points for drawing arc, ellipse equation coefficients | 27 |
Refer to Thesis.docx for full information on the algorithm and the results.