To validate models of sheet metal forming processes, experiments with sheets of metal marked with grids are performed. A method for measuring the deformed grid after processing is presented. It is based on morphological image processing and it requires four steps. A large top hat transformation is first applied to homogenize the grey level intensities of the background. The two main directions of the grid are then determined by calculating covariances. Linear filtering along the directions of the grid is used to extract a mask of the grid pattern. This mask is then skeletonized in order to extract the medial axis of the grid as well as its intersection points.
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