An integer arithmetic graphic line scan-conversion procedure sub-divides a pixel grid into a 1N sub-pixel grid, where N is a positive integer selected to provide a desired precision. In one embodiment, each decoder circuit element comprises equivalent components electrically connected in the same arrangement. The optical fiber includes a core having a desired diameter and a desired refractive index, the cladding surrounding the core and having a refractive index less than the, of the core or less than the outer cladding. The overall reduction in the size and cost of the swim fin is a secondary benefit to the reduction in work for the swimmer. Specifically, when the band-like paper is cut, the preceding knife and the following knife are given a specified amount of torque in the direction in which the preceding knife and the following knife are pressed against each other, by means of the preceding knife driving motor and the following knife driving motor.