An intermediate level vision system that utilises grey scale levels (typically 8 bits or 256 levels in our case) has been implemented which locates and links intensity discontinuities in a digitized image to subpixel precision. The discontinuities are located and localised by utilizing the zero crossings in the laterally inhibited image of the digitized picture.
P. J. MacVicar-Whelan,
T. O. Binford,
"Line Finding With Subpixel Precision", Proc. SPIE 0281, Techniques and Applications of Image Understanding, (12 November 1981); doi: 10.1117/12.965750; https://doi.org/10.1117/12.965750