1. A method for disparity cost computation for a stereoscopic image, comprising: computing partial path matching costs for a plurality of disparities of pixels of each of a plurality of parallelogram blocks of an image in a forward pass direction; between computing the partial path matching costs of the pixels of adjacent parallelogram blocks, computing partial path matching costs for the plurality of disparities of pixels along a boundary edge of a corresponding rectangular tile using paths that are external to the rectangular tile and computing partial path matching costs the disparities for all of the pixels of the corresponding rectangular tile; and computing total aggregated disparity costs for each disparity of the pixels of the image using the partial path matching costs computed for the pixels in the parallelogram blocks and in the rectangular tiles.