| 摘要 |
PURPOSE:To speed up rotation processing by 90 deg. by adopting an addressing method suitable for the conversion by 90 deg.. CONSTITUTION:Four picture elements belonging to the same, small square are added with the same address (m, n), and they are rotated by 90 deg.. Consequently this rotation is the same as a 90 deg. rotation in an N/2XN/2 image. If N is used instead of N/2, the way that the address changes from (m, n) to (m', n') can be obtained. In the case of the 90 deg. rotation, m'=-n+N/2-1 and n'=m hold. Equations m'=-m+N/2-1 and n'=-n+N/2-1 hold in a 180 deg. rotation, and equations m'=n and n'=-m+N/2-1 hold in a 270 deg. rotation. |
