In the field of font design, it is recommended to place points (control points) at the extreme points in the composition of curved lines. Extreme point refers to the position in which the angle of the handle used to draw a curved line is completely “horizontal (0 degrees)” or “vertical (90 degrees).” In terms of a circle, these would be the four points at the farthest edges of north, south, east, and west.

For example, in the italic “O,” the visual vertex is positioned diagonally. In terms of the data structure, points are often placed at the highest and lowest positions, and the left and right edge positions (extreme points) on the coordinates, apart from that visual vertex.

Having extreme points clarifies the outline structure, which makes post-processing more stable. As extreme points are also the basis for hinting processing, this plays an important role in terms of drawing quality.

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