A wheel alignment system, comprising: at least one imaging module (110, 112), each imaging module (110, 112) comprising: (a) an image sensor, for imaging a field of view encompassing a target (118, 120, 122, 124) attached to a wheel of a subject vehicle and generating representative image data; (b) a data communication interface; (c) a pre-processor, coupled to receive the image data from the image sensor, and configured to perform at least a gradient calculation on the image data from the image sensor, to form pre-processed image information; (d) a control coupled to the image sensor, the pre-processor and the data communication interface for controlling operations of the imaging module (110, 112); and (e) an illumination source coupled for selective activation by the control, for illuminating the target; the data communication interface being configured for transmitting said pre-processed image information from the pre-processor; and a computer coupled to receive the pre-processed image information transmitted from each imaging module (110, 112), and configured to act as a host computer of the wheel alignment system for processing the pre-processed image information to determine wheel alignment parameters of the vehicle, wherein the pre-processor is configured to perform a background subtraction, wherein the control selectively activates the image sensor to generate data representing a background image without illumination by the source and to generate data representing a foreground image of the field of view illuminated by the source; and wherein the pre-processor performs the background subtraction by subtracting the data representing the background image without illumination from the data representing the illuminated foreground image, wherein the pre-processor comprises a pipelined image processing circuitry; and wherein the pipelined image processing circuitry is configured to perform the background image subtraction, calculate a gradient magnitude for each respective pixel of data from a result of the background image subtraction to produce gradient information, and perform run length encoding on the gradient information to form compressed pre-processed image information for transmission to the host computer. at least one imaging module (110, 112), each imaging module (110, 112) comprising: (a) an image sensor, for imaging a field of view encompassing a target (118, 120, 122, 124) attached to a wheel of a subject vehicle and generating representative image data; (b) a data communication interface; (c) a pre-processor, coupled to receive the image data from the image sensor, and configured to perform at least a gradient calculation on the image data from the image sensor, to form pre-processed image information; (d) a control coupled to the image sensor, the pre-processor and the data communication interface for controlling operations of the imaging module (110, 112); and (e) an illumination source coupled for selective activation by the control, for illuminating the target; (a) an image sensor, for imaging a field of view encompassing a target (118, 120, 122, 124) attached to a wheel of a subject vehicle and generating representative image data; (b) a data communication interface; (c) a pre-processor, coupled to receive the image data from the image sensor, and configured to perform at least a gradient calculation on the image data from the image sensor, to form pre-processed image information; (d) a control coupled to the image sensor, the pre-processor and the data communication interface for controlling operations of the imaging module (110, 112); and (e) an illumination source coupled for selective activation by the control, for illuminating the target; the data communication interface being configured for transmitting said pre-processed image information from the pre-processor; and a computer coupled to receive the pre-processed image information transmitted from each imaging module (110, 112), and configured to act as a host computer of the wheel alignment system for processing the pre-processed image information to determine wheel alignment parameters of the vehicle, wherein the pre-processor is configured to perform a background subtraction, wherein