| 摘要 |
PROBLEM TO BE SOLVED: To plot a circle without trouble even on the orthogonal coordinate system of horizontal or vertical double accuracy. SOLUTION: The expansion of a circle is performed while using DDA processing for inputting vector data expressing the circle, storing the gradient corresponding value of the vector data in respect to respective coordinate values in the first axis direction of the orthogonal coordinate system specified by these vector data, changing one of coordinate values in the second axis direction of the orthogonal coordinate system at a time point, when the stored quantity exceeds a prescribed value, and forming dots along with the vector data by subtracting the prescribed value from the stored quantity. When executing DDA processing of the circle on the orthogonal coordinate system having different accuracy in the first and second axis directions, said DDA processing is executed by applying an ellipse having a longitudinal/lateral diameter ratio corresponding to the ratio of accuracy in the first and second axis directions as the vector data expressing the circle. |
