Computer Graphics and Image Processing最新文献

The distance transformation of a line pattern (DTLP) is discussed. The DTLP is a transformation of a binary pattern developed for extracting useful features to analyze and recognize a given pictorial data. The basic type (BDTLP) has already been reported; a modification and a generalization of the BDTLP is presented. The modified DTLP (MDTLP) is derived by defining an inhibited edge point among the edge points of an input line pattern. By applying the MDTLP, information on the length of a line pattern is concentrated on the inhibited edge point instead of the center point as in the case of the BDTLP. The generalized DTLP (GDTLP) is a parallel iterative local operation applied to a line pattern with gray values, whose execution is controlled by the BDTLP or the MDTLP performed on another picture plane containing a binarized version of an input line pattern. It enables one to process a line pattern with arbitrary gray values on it as well as a binary pattern. Experimental results are shown concerning the application of the GDTLP to the processing of ridge and ravine lines extracted from a digitized map data. An application of the type II MDTLP to the extraction of information on the loop structure of a line pattern is also presented with illustrative examples.

In understanding pattern analysis and image processing by the visual system we are mainly concerned with receptive field modeling of the cells in the X channel. Each of the three physiological levels of the visual pathway (retina, lateral geniculate bodies, and striate cortex) is characterized by the overlapping of cell receptive fields on the visual space. We propose a multilayer model based on this overlapping that explains the decreasing of the overlap factor and also the size constancy. Besides, a homogeneous distribution of the X-type ganglion receptive fields in each layer of our model, allows us to obtain, by a parallel and serial of cortical receptive fields of different orders. We call them sign configurations. They application of a simple transform (elementary connecting process, ECP, a systematic representation some specific properties: symmetry, orientation, periodicity, and complexity. If an inhibitory mechanism is assumed, these sign configurations can present the spatial frequency characteristics of a Fourier analyzer.

A method is presented for eliminating spurious brightness discontinuities, or false contours, in areas in which brightness varies gradually, while preserving edge sharpness. The basic idea of the method is to randomly blur points only in the neighborhood of each border on which those spurious brightness discontinuities may occur. The method is used for producing natural appearance of a picture for the human eye, not for picture analysis.

A new, effective way of storing octtrees for three-dimensional representation of objects is given. The 10 fields normally required to identify a node of an octtree are reduced to only one. Algorithms are presented for (i) mapping cubic pixels from and to space array (with subscripts I, J, K), (ii) finding the stereographic projections on the IJ, IK, and JK planes, (iii) performing union (intersection) of two objects centered on the same array, and (iv) finding the pixel adjacent to a given one in a specified direction. The newly proposed data structure is a (dynamically built) array of sorted octal codes which reflects the successive octant subdivisions; it represents a dramatic improvement with respect to octtrees when space complexity is considered. Also, the formulation of the procedures mentioned above takes advantage of this “natural” structure and results in very simple algorithms, easy to code and optimize. Some of the proposed procedures could also be implemented in parallel mode.