1. A computer-implemented method, comprising under control of one or more computer system configured with executable instructions, obtaining image data from a camera of a portable computing device; determining at least one feature point of the image data using a feature point detection algorithm; applying a saliency function to the at least one feature point to determine at least one corresponding saliency value for at least a portion of the image data, wherein the saliency function is a feature point density function programmed to calculate a number of feature points per area, areas with a higher density of feature points having a higher saliency value relative to areas with a lower density of feature points; generating a saliency map of the image data based at least in part on the at least one corresponding saliency value; determining at least one region of the saliency map in which the at least one corresponding saliency value meets or exceeds a saliency threshold value; and selecting the at least one region of the saliency map to be analyzed using a visual recognition component.