Methods, machines, and computer-readable media storing machine-readable instructions for segmenting pixels in an image are described. In one aspect, a region of background pixels is identified in the image. At least some of the background pixels in the region are located on a boundary spatially delimiting the region. One or more orientation-dependent adaptive thresholds are determined for one or more respective candidate growth directions from a given background pixel located on the region boundary. Color distances between the given background pixel and candidate pixels in a neighborhood of the given background pixel are determined. The region is grown based on application of the one or more orientation-dependent adaptive thresholds to the determined color distances.