Fig. 2.

Operational definition of relevance (target similarity) and edge energy. A: relevance maps were obtained by convolving the target and its quadrature phase shift with the natural scene and then taking the sum of their squares. B: edge-energy maps were computed by taking the sum of squares of horizontal and vertical edge gradients. Before computing the relevance and energy maps, the image was degraded in accordance with decreasing visual acuity in the periphery, with respect to an example fixation location shown as a yellow crosshair [adapted from Ramkumar et al. 2015].