Digital Image Processing techniques have become increasingly popular in the last few years. Conventional silver halide photography continues to be used by the large amateur market, but not without "imperfect" images. There is almost always a need for enhancement or subsequent improvement after the photograph is made. This study dealt with computer image enhancement of such "imperfect" photographs using homomorphic (non-linear) and linear frequency-domain digital filtering (on a VAX-11/785) and a comparison in effectiveness was determined, using a subjective criteria for image quality. It was found that, in general, linear filtering is to be the preferred method of choice when implementing image enhancement on amateur type photographs. Differences in "image quality improvement" by the two techniques was minimal, when the image was subjected to histogram equalization after processing. Homomorphic filtering requires substantial post processing without which it is a potential failure. Linear filtering was both computationally less demanding and subjectively more pleasing.
Library of Congress Subject Headings
Images, Photographic; Image processing--Digital techniques; Digital filters (Mathematics); Photography--Retouching
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
Sampat, Nitin, "Computer enhancement of real world photographic images using homomorphic and linear filtering" (1985). Thesis. Rochester Institute of Technology. Accessed from
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