Comparing shoeprints using semi-automated methods requires that all images be registered to a common 2D “space”. For this research, a simple translation and rotation is considered sufficient to accomplish full image registration. The series of images on the right illustrate the result of registration for two shoes of the same size. The original image shows a 600-PPI digital scan of a shoeprint, including contrast reversal (Ref. Manal Khalil, 2011). The rightmost image in the series depicts the same image, but after registration. The original image has been padded on all sides, translated to ensure that a single feature in the image resides at a common (x,y) coordinate, and then rotated about the translation point to ensure that the details of the tread pattern distribute along orthogonal N-S and E-W axes. The central image overlays the registered scan with a baseline print used to represent the common 2D “space”. This overlay illustrates the agreement between the registered image and a “master print”.
The second series of images illustrate the same registration process, but for a shoe several sizes smaller than the master print. The overlay illustrates that the smaller shoeprint is coincident with the master print at the translation point and that all features are distributed along N-S and E-W orthogonal axes, but naturally all features will not agree since the overlaid shoes are of different sizes.
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