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The Sensory-Interactive Robotics Group at the National Bureau of Standards is producing PIPE, a pipelined image-processing engine, for research in low-level machine vision. PIPE processes sequences of images at field rates through a series of point and neighborhood operations. It is divided into a variable number of identical stages, each of which performs an independent set of operations on the image data stored in the stage. A stage control unit determines the sequence of operations performed within a stage on each image. This sequence is easily modified by a host computer during the inter-field interval when all of the stage control units can be totally reconfigured. Images flow through PIPE in several ways. In addition to the (standard pipeline) "forward" pathway, where an output image is sent to the next stage, an output image can also be sent to the same stage via a "recursive" pathway and to the previous stage via a "retrograde" pathway. As a result, PIPE can support relaxation operations, temporal neighborhood operations, and other local operations. Several processing modes are available in PIPE in addition to the usual "SIMD" mode of pipelined processors. In an "MIMD" mode, one of several operations is performed on a region of interest which can be defined by the host device or by previous image operations. PIPE also supports variable resolution pyramids where an image is compressed or expanded as it passes between stages.