1 June 1990 Effect of noise and MTF on the compressibility of high-resolution color images
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Abstract
There are an increasing number of digital image processing systems that employ photographic image capture; that is, a color photographic negative or transparency is digitally scanned, compressed, and stored or transmitted for further use. To capture the information content that a photographic color negative is capable of delivering, it must be scanned at a pixel resolution of at least 50 pixels/mm. This type of high quality imagery presents certain problems and opportunities in image coding that are not present in lower resolution systems. Firstly, photographic granularity increases the entropy of a scanned negative, limiting the extent to which entropy encoding can compress the scanned record. Secondly, any MTFrelated chemical enhancement that is incorporated into a film tends to reduce the pixel-to-pixel correlation that most compression schemes attempt to exploit. This study examines the effect of noise and MTF on the compressibility of scanned photographic images by establishing experimental information theoretic bounds. Images used for this study were corrupted with noise via a computer model of photographic grain and an MTF model of blur and chemical edge enhancement. The measured bounds are expressed in terms of the entropy of a variety of decomposed image records (e.g., DPCM predictor error) for a zeroeth-order Markov-based entropy encoder, and for a context model used by the Q-coder. The resultsshow that the entropy of the DPCM predictor error is 3-5 bits/pixel, illustrating a 2 bits/pixel difference between an ideal grain-free case, and a grainy film case. This suggests that an ideal noise filtering algorithm could lower the bitrate by as much as 50%.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul W. Melnychuck, Paul W. Melnychuck, Michael J. Barry, Michael J. Barry, Michael S. Mathieu, Michael S. Mathieu, } "Effect of noise and MTF on the compressibility of high-resolution color images", Proc. SPIE 1244, Image Processing Algorithms and Techniques, (1 June 1990); doi: 10.1117/12.19515; https://doi.org/10.1117/12.19515
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