Clip circuit for CRT display unit.

摘要

An ALU (82) in a CRT display unit performs calculation based on line segment data provided from a line segment data providing circuit (20) and data representing a border line provided from an area data providing circuit (21) to obtain a ratio of a distance between the start point coordinates and the end point coordinates of the line segment to a distance between the start point coordinates or end point coordinates and a border line of a predetermined area. When it is determined that the calculated ratio is larger than a predetermined value, the ALU (82) sets new coordinates in the vicinity of a point of intersection between the line segment and the border line of the predetermined area instead of the start point coordinates or the end point coordinates of the line segment. Then, based on the newly set coordinates and the data representing the border line, the ALU (82) calculates by a middle point division method, a point of intersection between a line segment connecting the newly set coordinates and start point coordinates or end point coordinates and the border line. Thus, the time required for a middle point obtained by division to approach the border line can be shortened.