Table 1. Tuning of the hand-designed methods that depend on parameters.
| Method | Tuned parameters | ||
|---|---|---|---|
| Symbol | Grid search domain | Optimal value | |
| Felzenswalb | s | {0.5, 1.0, 2.0, 4.0} | 2.0 |
| Flood fill | d | {1, 2} | 1 |
| τ | {2, 4, 8, 16} | 16 | |
| K-means | k | {4, 8, 12, 16} | 8 |
| MorphACWE | Ni | {10, 20, 40} | 10 |
| λ1, λ2 | {1.0, 2.0, 4.0} | 1.0, 4.0 | |
| MorphGAC | Ni | {10, 20, 40} | 10 |
| fb | {−0.5, −1.0, −2.0, −4.0} | 0.5 | |
| MSER | ∆ | {2, 4, 6, 8} | 2 |
| MultiOtsu | N | {3,4} | 4 |
| SLIC | k | {4, 8, 12, 16} | 16 |
| c | {0.1, 1.0, 10.0, 100.0} | 1.0 | |
| Watershed | r | {2, 3, 4} | 2 |
| c | {0.1, 1.0, 10.0, 100.0} | 0.1 | |
The optimal values were determined through grid search over the train and validation sets using DSC as the target metric. For the meaning of symbols please refer to the specific sections. Key to symbols (from top to bottom): s = scale of observation; d = connectivity; τ = tolerance; k = number of clusters; Ni = number of iterations; λ1, λ2 = user-defined functional parameters; fb = baloon force; ∆ = threshold range; N = number of classes; r = radius of the circular neighbourhood; c = compactness. MorphACWE, morphological active contours without edges; MorphGAC, morphological geodesic active contours; MSER, maximally stable extremal regions; SLIC, simple linear iterative clustering; DSC, Sørensen-Dice coefficient.