Aliasing in minification of digital images

Sampling is a necessity in minifying a digital image. In the event that the image contains spatial frequencies higher than half the sampling frequenci es in any dimensions, aliasing will occur. Aliasing in minifying digital im ages with and without prefiltering are compared. Using the Shannon sampling theorem, the reduction of aliasing is explained based on the Fourier trans form, instead of the discrete wavelet transform. It is found that one shoul d not consider only the classical quality evaluation measures of the sample d image when selecting from the several antialiasing methods, we should als o consider the particular requirements of some key local information, such as to make letters or Chinese characters more recognizable, although the de gree of aliasing reduction may be lowered. (C) 2001 Society of Photo-Optica l Instrumentation Engineers.