region growing

Growing a segmented region outward from a seed pixel, admitting each neighbor only while it stays close to the region's own running mean.

Region growing starts from one or more seed pixels and repeatedly admits an adjacent pixel into the region when $|f(\text{neighbor}) - \bar f_{\text{region}}| \le \tau$ for a chosen tolerance $\tau$ , updating the region's own running mean after each admission, until no remaining neighbor qualifies. Unlike thresholding, the decision is relative to the growing region's own local statistics, not a fixed rule tested independently at every pixel.