The design, implementation, and application of a CMOS VLSI custom chip for real-time centroid calculation of digital images is described. Finding the centroid coordinates of objects in digital images is useful, especially in applications that involve the tracking of moving objects in a scene. The input signal to the chip is a raster-scanned digitized image. The chip first calculates the zeroth and first two-dimensional moments of the input image and then two division operations are performed to get the x and y coordinates of the centroid. A particular application of this chip for drawing extremely fine lines and curves on a high-resolution CRT display with a lightpen is reported. The chip is used to calculate the centroid coordinates of a patch of light seen by the lightpen's photosensor. The chip has been fabricated in 2. 5- mu m CMOS technology. It has been tested and is fully operational.
