| 摘要 |
PURPOSE:To draw the thick lines free from the omission of white in a small memory capacity even when the start or end coordinates are inputted out of a drawing area by setting a coordinate conversion area at the outside of the drawing area with the width larger than the width of a thick line by half or more. CONSTITUTION:A rectangle O'A'B'C' is defined as a coordinate conversion area including a drawing area OABC increased by 1/2 line width. Then the coordinates of intersections S' and E' between a segment SE connecting the input start and end coordinates S and E and the outer boundary line of the coordinate conversion area are obtained. Then the data on both coordinates S and E are replaced with the obtained coordinate data on the intersections S' and E' and defined as the processing start and end coordinates. Then a segment S'E' is used as a reference segment of the thick line, and the line thickening processing is carried out to increase the line width at both sides of the reference segment by half l/2 of the line width. Then only the drawing area is displayed for drawing a thick line. Thus it is possible to effectively draw a thick line free from the omission of white within the drawing area in a small memory capacity. |
