1. A method of processing two-dimensional image data, comprising: receiving a plurality of images, wherein each image represents a two-dimensional field of view, and wherein one of the images is a reference image; and using at least one processor to apply a second derivative operator to digital data corresponding to the plurality of images, to generate therefrom a second-derivative epipolar plane image, identify at least one item appearing in the reference image, for each identified item, generate from the second-derivative epipolar plane image a depth estimate for at least one point corresponding to the identified item, each depth estimate representing depth of the corresponding point in a dimension independent from the two-dimensional field of view represented by the reference image, and store each depth estimate in processor-accessible memory; wherein the second derivative operator comprises a matrix operator, using the at least one processor to apply the second derivative operator to the digital data comprises convolving the matrix operator with the digital data, to generate second derivative data, and storing the second derivative data in the processor-accessible memory, and using the at least one processor to generate the depth estimate for the at least one point comprises processing the second derivative data to identify therefrom at least one edge, each edge corresponding to a zero-crossing in the second derivative data.