Figure 1. Illustration of the mean-shift model.

A. Initialization of the generic kernel based on the user-defined position (x’₀,y’₀).

The kernel (here an octagon, ndir = 8) is divided into sectors (S1 to S8), each one containing two nested triangle-shaped regions (R_b and R_w), one sensitive to dark and the other to bright pixels (“b” means “black” and “w” means “white”). Here, R_b6 and R_w6 are shown, with a total of 16 regions (R_b1 to R_b8 and R_w1 to R_w8). Only the contours of sectors 2-5 are shown in order to lighten and better visualize the figure. The cell is not presented for clarity.

B. Adjustment of the position of the center at t₀.

Sixteen mass centers (g_b1 to g_b8 and g_w1 to g_w8) are first calculated from the intensities of the pixels from each region, (g_b1 and g_w1 are shown). Sector mass centers (C) are calculated from g_wn and g_bn, (C₈ is shown as an example). The center (x₀,y₀) is defined as the centroid of the mass centers C₁ to C₈.

C. Adaptation of the kernels to cell morphology at t₀.

The distances (d_i) between each mass center (g_wn) and kernel center (x₀,y₀) are calculated (d₈ is shown as an example). The new outer radii (r_wn) are calculated based on d_n, the average d_n distances, the expansion factor and the anisotropy factor. r_bn is assigned according to the ratio (r_b / r_w), which is initially defined by the user.

D. Representation of the kernels at t₁.

Information is obtained applying the processes explained in B and C. The size of the sectors will increase or decrease (indicated by the arrows) as a function of cell shape modifications.