Figure 1: Stages of image processing. (a) Detail of a video micrograph of the (111) plane of a face-centered cubic colloidal crystal. The radius of each polystyrene sulfonate spheres is m. The nearest neighbor spacing is roughly 1 m. (b) The same image filtered with the convolution kernel in eqn. (4). (c) Gray-scale dilation of the image in (b). Dark spots represent the initial estimates for particle locations based on the neighborhood maximum algorithm. (d) Final particle location estimates. The lines connecting sites constitute the network of nearest-neighbor bonds computed as a Delaunay triangulation [F. P. Preparata and M. I. Shamos, Computational Geometry (New York, Springer-Verlag, 1985)]. Such a network is useful as the basis of many measurements of local ordering.