| 摘要 |
A system and method of rendering a curve using data look-up tables for rasterizing the curve. The curve is subdivided so that it is approximated by a series of straight line segments of approximately equal length, with no line segment exceeds tw o pixels in length. The system subdivides any line segment that crosses horizontal axis of two adjacent horizontal scan rows. If the line segment does not cross the horizontal axis of a scan row, the pixel does not require detailed analysis. If the line segment does cross the horizontal axis of a particular horizontal scan row, the system uses look-up tables to determine the distance from the center point of the pixel in winch the line segment crosses the horizont al axis to the point at which the line segment crosses the horizontal axis. The system uses three indices as pointers to the data look-up table containing the desired data. The three indices are themselves pointers to separate index tables in which the multiplication calculations required for the data look-up table have been precalculated and are incorporated into the values stored in the index tables. The index tables also incorporate a reduction in resolution from 1/64 to 1/8 pixel resolution. The index tables are also nonlinear to allow more data entries in areas where the round off error resulting from the resolution reduction are greatest. If the line segment crosses the horizontal axis to the left of the center of a pixel, th e logic state for the pixel is changed. The system can be implemented on any computer and operates with any raster scan graphics display unit.
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