Binning compensation filtering techniques for image signal processing

Abstract

Various techniques for applying binning compensation filtering to binned raw image data acquired by an image sensor are provided. In one embodiment, a binning compensation filter (BCF) includes separate digital differential analyzers (DDA) for vertical and horizontal scaling. A current position of an output pixel is determined by incrementing the DDA based upon a step size. Using the known output pixel position, a center source input pixel and an index corresponding to the between-pixel fractional position of the output pixel position relative to the input pixels may be selected for filtering. Using the selected center input pixel, one or more same-colored neighboring source pixels may be selected. The number of selected source pixels may depend on the number of taps used by the scaling logic, and may depend on whether horizontal or vertical scaling is being applied. Using the selected index, a set of filter coefficients may be selected from a filter coefficient lookup table, applied to the selected source pixels, and the results may be summed to determine a value for an output pixel having a position corresponding to the current position of the DDA. This process may be repeated for each input pixel and may be performed in both vertical and horizontal directions, thus ultimately producing a re-sampled set of image data that is spatially evenly distributed.