Area of image processing which deals in separating an image's regions. For example, a microscope image of a group of cells could need segmentation to count the number of visible cells, average size or similar measures.

Segmentation is usually carried out detecting contours, using different approaches. If we treat an image like a height field, then the derivatives would give us an approximation of contours (a high derivative means a high slope, which is characteristic in a contour). Further refinements include the gradient and the laplacian.

Morphological image processing also lets us find contours of the image, particularly by approximating the gradient of the image (for example, substracting the erosion from the dilatation), or by using watersheds.

Another common technique is blurring the image (convolutioning with a gaussian, for example) before segmentation, as many annoying quirks in the image can be removed that way.

Seg`men*ta"tion (?), n.

The act or process of dividing into segments; specifically Biol., a self-division into segments as a result of growth; cell cleavage; cell multiplication; endogenous cell formation.

Segmentation cavity Biol., the cavity formed by the arrangement of the cells in segmentation or cleavage of the ovum; the cavity of the blastosphere. In the gastrula stage, the segmentation cavity in which the mesoblast is formed lies between the entoblast and ectoblast. See Illust. of Invagination. -- Segmentation nucleus Biol., the body formed by fusion of the male and female pronucleus in an impregnated ovum. See the Note under Pronucleus. -- Segmentation of the ovum, ∨ Egg cleavage Biol., the process by which the embryos of all the higher plants and animals are derived from the germ cell. In the simplest case, that of small ova destitute of food yolk, the ovum or egg divides into two similar halves or segments (blastomeres), each of these again divides into two, and so on, thus giving rise to a mass of cells (mulberry mass, or morula), all equal and similar, from the growth and development of which the future animal is to be formed. This constitutes regular segmentation. Quite frequently, however, the equality and regularity of cleavage is interfered with by the presence of food yolk, from which results unequal segmentation. See Holoblastic, Meroblastic, Alecithal, Centrolecithal, Ectolecithal, and Ovum. -- Segmentation sphere Biol., the blastosphere, or morula. See Morula.


© Webster 1913.

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