| 摘要 |
PURPOSE:To attain high speed processing by executing clip processing for discriminating a retrieval line segment which intersects with a specified line segment on a graphic screen. CONSTITUTION: When information on start and end points A and B of the specified line segment is given to a CPU70 from a computer 10, the CPU70 retrieves a FIGURE in a graphic memory 60. When the FIGURE can be found, minimum and maximum values of the retrieval line segment are checked, and judgment is made whether or not the retrieval line segment (f) lies in a rectangle F with the specified line segment AB as an diagonal according to said values. Where points cannot be obtained in the rectangle F, the retrieval line segment (f) is segmented at an overlapped part by the rectangle F and a rectangle G with the retrieval line segment (f) as a diagonal, and both end points of the segmented retrieval line segment are assumed to be f1 and f2, respectively. When the start and end points of the retrieval line segment are not positioned at the same side of the specified line segment, the specified line segment AB comes to intersect with the retrieval line segment (f), and therefore the name of the retrieval line segment (f) is stored in an output buffer 80. Thus the discrimination can be carried out at a high speed compared with the case where a line segment is discriminated by calculation with use of an advanced language.
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