This is accomplished by sub-sampling pixels in the image in a manner proportional to the digital zoom level. For example, in a 4 megapixel camera (2048 x 2048) utilizing RPDZ - like some JAI cameras, four zoom modes are offered. The full FOV is imaged by capturing every fourth pixel in every fourth row, thus creating a 512 x 512 resolution. (See Fig.).
As the image is digitally zoomed through the other three modes, the sub- sampling rate is adjusted to maintain the same pixel density until it reaches the center 512 x 512 pixels of the image. It can also be used in multi-camera network scenarios where digital zooming is required but network bandwidth is limited.