摘要:

The problem of two-dimensional recursive digital filtering of large images by the sectioning (or block-mode) technique has been considered. It has been stated that, if the impulse-response sequence of the recursive digital filter dies down relatively sharply, by a suitable truncation, the available sectioning techniques can be used to perform the filtering operation, as with nonrecursive filters. An analytical approach is presented which formulates the upper bound on the norm of error resulting from the application of truncation. This bound is found to be independent of the size of blocks. In addition, an expression for the computation time is obtained, when a mixed radix two-dimensional FFT is used. Using these expressions, a simple procedure for minimising the truncation error and computation time is suggested which determines suitable values of the parameters involved. The effectiveness of the optimisation procedure developed here has been examined for smoothing operation of an X-ray image on a CDC 6500 computer.

DOI:10.1049/ip-f-1.1982.0056

出版商:IEE    

年代:1982

数据来源: IET

摘要:

Our society has become highly dependent on its modern communications systems, e.g. the radio, television, telephone, telex, facsimile, high-speed data links etc. A high proportion of the information disseminated over these communications circuits is confidential in nature. In these situations the communicants should take steps to conceal the content of a message from not only the casual listener but also the determined interceptor. There is little doubt that this problem of protecting and securing communications will continue to grow at an increasing rate over the coming years, not only in its traditional military role but also in the public and commercial domains. The paper considers the type of cryptographic systems available today. As well as discussing the mathematical and statistical requirements of such systems, it explores how, with careful design, most of these needs can be met while the complexity of the hardware implementation is kept to a minimum.

DOI:10.1049/ip-f-1.1982.0057

出版商:IEE    

年代:1982

数据来源: IET