In some examples, a sensor apparatus comprises: an array of pixel cells configured to generate a charge in response to light and convert the charge to output a voltage of an array of voltages, one or more an analog-to-digital converter (ADC) configured the convert the array of voltages to first pixel data comprising one or more pixel values, and an on-sensor controller configured to receive the first digital pixel data from the ADC, determine first pixel values and second pixel values, generate second digital pixel data comprising the first pixel values and not the second pixel values, and send the second digital pixel data off-sensor. The on-sensor controller may generate a control signal to alter the rate of charge generation by the array of pixel cells. The digital image data may be generated using a compressed map of pixels.