2D-Histogram Lookup for Low-contrast Fault Processing

This paper presents a framework for low-contrast texture fault processing based on 2D-Histogram lookup. 2D-Histogram lookup is a variant of 2D-Lookup operation. For 2D-Lookup, in two differently processed versions of the same image, grayvalue pairs from the same location in both images are replaced by the corresponding entry in a given two-dimensional matrix. The two operations and the matrix have to be provided for full algorithm specification. For 2D-Histogram lookup, the matrix is derived from the 2D-Histogram of both processed images. The main advantage of using the 2D-Histogram is the darkening of rarely occurring structures in the image, while highly probable image structures becomes bright. The so-processed images are then given to a 2D-Lookup procedure for automatic filter generation. For low-contrast texture faults, i.e. faults which are hard to separate from the background texture, the approach shows better performance in fault region detection than the approach of 2DLookup adaptation without 2D-Histogram lookup. For handwriting separation from textured background, no achievement was obtained.