1. A computer-implemented process for segmenting and estimating the optical flow between a pair of images of a scene, comprising using a computer to perform the to following process actions: establishing an initial segmentation for each image; establishing an initial optical flow estimate for each segment of each image, wherein the optical flow estimate is the estimate of a translation that describes any movement of the segment from a position in one of the images to a position of the segment as seen in the other image; computing a refined optical flow estimate for each segment of a first one of the images from the initial segmentation of that image and the initial optical flow of the segments of that image; computing a refined optical flow estimate for each segment of the second image from the initial segmentation of that image and the initial optical flow of the segments of that image; refining the segmentation of the first image from the last-computed optical flow estimates for each segment of the first image; refining the segmentation of the second image from the last-computed optical flow estimates for each segment of the second image; further refining the optical flow estimates for each segment of the first image from the last-computed segmentation of the first image; further refining the optical flow estimates for each segment of the second image from the last-computed segmentation of the second image; and iteratively repeating process actions of refining of the segmentation of the images followed by the process actions of refining the optical flow estimates for each segment of the images until a prescribed number of iterations have been completed, wherein, all of the pixels of the images are assigned to a main segment in that image, and except in the initial segmentation, those pixels of the images that contribute color to a lesser extent to a second segment in that image are also assigned to a secondary segment, and the process actions of refining the segmentation of the images from the last-computed optical flow estimates for each segment of that image, comprise the actions of, for every pixel in each image, identifying the segments having pixels which fall within a prescribed-sized pixel neighborhood surrounding the pixel under consideration using the last-computed segmentation of the image as a basis, designating as candidate segments those identified segments which are the main segment for a pixel in the pixel neighborhood, whenever more than one segment is designated as a candidate segment for a pixel under consideration, identifying a winning pair of candidate segments which represent the closest in color and physical distance to the pixel under consideration, computing an alpha value for the pixel under consideration which represents the percentage of the color of the pixel contributed to the segment of the winning pair which is closest in color to the pixel and assigning the alpha value to the pixel, assigning the pixel under consideration to the segment of the winning pair which is closest in color to the pixel and designating the segment as the pixel's main segment, and assigning the pixel under consideration to the other segment of the winning pair which is not the closest in color to the pixel and designating the other segment as the pixel's secondary segment, and whenever only one segment is designated as a candidate segment for a pixel under consideration, assigning the pixel under consideration to the segment and designating the segment to be the pixel's main segment, and assigning an alpha value of 1 to the pixel under consideration.