
References
265
[46],
and Haralick et al. [16]; see also the references on tapered and opti-
mum quantization in Section 4.4.
Much work on image enhancement, including both gray scale and geo-
metric correction techniques, as well as filtering techniques for sharpening
and smoothing, has been done at NASA's Jet Propulsion Laboratory; see,
e.g., O'Handley and Green [35].
The use of derivative operations for sharpening a picture is very old (e.g.,
Goldmark and Hollywood [13]; Kovasznay and Joseph [24, 25]). A more
recent review by Prewitt [40] also discusses Laplacians and their modifica-
tions (those based on the second derivative in the gradien ...