A dual/multi-energy x-ray image sensor with stacked two-dimensional pixel arrays. Each pixel in one pixel array has a corresponding “overlaid” pixel in the other pixel array. The pixel arrays are stacked parallel and aligned so that they are nominally normal to the x-ray path, and so that a straight path taken by an x-ray photon from the x-ray source to a pixel in one pixel array will also nominally intersect the corresponding pixel in the other pixel array(s). The energy image sensor provides an x-ray scanning detector system, which has increased signal levels and signal-to-noise ratios over dual- or multi-energy detectors using linear diode arrays, specifically when the pixel arrays are TDI pixel arrays that offer higher sensitivities in high-speed line-scan applications. Signal processing circuitry is placed on a periphery of the pixel arrays and shielded. Dual-to-multiple energy applications can be accomplished by increasing the number of stacked pixel arrays.