Frequency domain analysis of two-pass rotation algorithm

The rotation of a digital image is a computer graphics transformation which is increasingly used in the video industry. Because of the apparent unordered nature of this geometric transformation, it seems that two full frame buffers would be needed. Recently Catmull and Smith [1] have proposed a two-pass algorithm which overcomes this difficulty by constraining all manipulations to be limited to either vertical or horizontal scanline. An important property of this transformation is that it can be done "in-place" with an extra video line buffer. In this paper we will analyze this rotation algorithm viewed as a two-dimensional linear transformation. In particular we will investigate its effects on the spectrum of the image being transformed. Theoretical and simulation results will be presented.