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Abstract:
Image Pyramids are frequently used in porting non-local algorithms to graphics
hardware. A Histogram pyramid (short: HistoPyramid), a special version
of image pyramid, sums up the number of active entries in a 2D
image hierarchically. We show how a HistoPyramid can be utilized as an implicit indexing data
structure, allowing us to convert a sparse matrix into a coordinate list
of active cell entries (a point list) on graphics hardware . The algorithm
reduces a highly sparse matrix with N elements to a list of its M active
entries in O(N) + M (log N) steps, despite the restricted graphics
hardware architecture. Applications are numerous, including feature
detection, pixel classification and binning, conversion of 3D volumes to
particle clouds and sparse matrix compression.
