1. A target detection device for detecting predetermined targets that are captured within an image, the device including: a target region identification device that is configured to identify a region of interest in the captured image, the region of interest including a target having geometries consistent with the predetermined targets; and a classification device that is configured to determine whether the region of interest includes the predetermined targets by analyzing the region of interest with a strong classifier descriptor that describes at least one of shape attributes and appearance attributes that are characteristic of the predetermined targets, wherein the strong classifier descriptor is based on a linear weighted combination of a subset of weak classifier descriptors, and the subset of weak classifier descriptors is selected from a plurality of weak classifier descriptors that each describe at least one of shape attributes and appearance attributes that are characteristic of parts of the predetermined targets, and wherein the subset of weak classifier descriptors includes at least one user-defined weak classifier descriptor that is defined by a user based on database images including the predetermined targets.