An imager tile including four-side buttable sub-imager pixel arrays with on-chip digitizing electronic readout circuit. Pixel groupings formed from among the plurality of imagers. Readout electronics including a buffer amplifier for each of the pixel groupings are connected to respective outputs of buttable imagers. Shared analog front ends connect to respective buffer amplifiers of pixel groupings. An analog-to-digital converter at a common centroid location relative to the shared analog front ends includes three data lines—selection input/output line to individually select an output, a clock input line, and a shared digital output line. A pixel output from a respective buffer amplifier is addressable by data provided on the selection input/output line, and the pixel output is provided on the shared digital output line. The I/O lines connected to a programmable logic device where the imager serial data input is output as a massively parallel data stream.