Multi layered image enhancement technique

摘要

A system for enhancing an input image including receiving an input image and filtering the input image with a plurality of non-linear smoothing filters providing a respective plurality of filtered outputs. The system processes a plurality of the filtered outputs with respect to at least one of another of the filtered outputs and the input image to determine a plurality of detail layers. The system filters the plurality of detail layers with a plurality of non-linear smoothing filters providing a respective plurality of smoothed layers. The system adjusts the plurality of smoothed layers in such a manner that regions closer to an edge are enhanced to a lesser extent than regions farther from an edge and combining the adjusted the smoothed layers to provide an enhanced output image.

主权项

1. A method for enhancing an input image comprising:
(a) receiving an input image; (b) filtering said input image with a first non-linear filter that attenuates regions of input image proximate edges to an extent less than regions of said input image not proximate said edges to provide a first filtered image;
(i) where said first non-linear filter filters a first pixel of said input image by calculating a first value as the summation of (1) a left pixel weighting multiplied by a left pixel input, (2) a first pixel weighting multiplied by a first pixel input and (3) a right pixel weighting multiplied by a right pixel input, wherein the left pixel weighting corresponds to a pixel to the left of said first pixel of said input image, the first pixel weighting corresponds to said first pixel of said input image, and a right pixel weighting corresponds to a pixel to the right of said first pixel of said input image,(ii) calculating a second value as said first value divided by the summation of (1) said left weighting of said left pixel, (2) said first pixel weighting of said first pixel, and (3) said right weighting of said right pixel,(iii) said left weighting of said left pixel is determined using a look up table based upon the absolute value of the difference between said first pixel and said left pixel,(iv) said right weighting of said right pixel is determined using said look up table based upon the absolute value of the difference between said right pixel and said first pixel,(v) where said look up table has a first value when said absolute value of the difference between said first pixel and said left pixel is less than a first threshold, where said look up table has a second value when said absolute value of the difference between said first pixel and said left pixel is greater than said first threshold and less than a second threshold; and where said look up table has a third value when said absolute value of the difference between said first pixel and said left pixel is greater than said second threshold,(vi) where said look up table has a third value when said absolute value of the difference between said first pixel and said right pixel is less than a fourth threshold, where said look up table has a fourth value when said absolute value of the difference between said first pixel and said right pixel is greater than said fourth threshold and less than a fifth threshold; and where said look up table has a fifth value when said absolute value of the difference between said first pixel and said right pixel is greater than said sixth threshold; (c) processing said first filtered image by determining a comparison between said first filtered image and said input image that has not been filtered by said first non-linear filter to provide a difference filtered image; (d) filtering said difference filtered image with a second non-linear filter that reduces the amount of noise in said difference filtered image in a manner not dependent on the content of said difference filtered image to provide a second filtered image; (e) processing said second filtered image by determining a comparison between said second filtered image and said input image to provide an enhanced output image.