Images are filtered by the various stages of visual processing and undergo a perceptual transformation. To begin to quantify this process, the appearance of sinewave gratings, images with a sinusoidal luminance profile, was studied. The most salient features of these images is that at high contrast they do not in general appear sinusoidal. A logarithmic transform, based on Fechner's law, is suggested as a first approximation to the perceptual transform in the luminance domain, and shown to characterize the apparent luminance profiles of sinewave gratings. Furthermore, the sinusoidal image profile can be pre-processed (inverse transformed) to create a new image which, when viewed, reverses to a large extent the perceptual distortions discussed above. This `corrected' image would appear as if the combined effects of the perceptual transform had not acted, making the now non-sinusoidal profile conform much more closely to our symmetrical expectations of a sinusoidal appearance. The principle of inversion used here is suggested as a general way of testing the validity of some human vision models proposed to achieve better image processing algorithms based on visual perception.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Adar Pelah, Adar Pelah, } "Inverting the perceptual transform", Proc. SPIE 2179, Human Vision, Visual Processing, and Digital Display V, (1 May 1994); doi: 10.1117/12.172659; https://doi.org/10.1117/12.172659

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