ON TEXTURE ANALYSIS - LOCAL ENERGY TRANSFORMS VERSUS QUADRATURE FILTERS

The well-known method proposed by Laws for texture analysis first subj ects the texture to a filter bank, followed by the computation of ener gy measures, e.g. through local variance estimation. As shown by Unser in 1986, the filter bank application is equivalent to a linear transf ormation of the grey values of neighbouring pixels. In this contributi on, we derive a further linear relationship between the local variance s of the filter outputs and the autocorrelation function of the textur e process. Furthermore, we examine how the filter bank approach is rel ated to another method based on multifiltering, namely that one using quadrature filter pairs, by means of which the amplitude envelopes of the filtered texture signal can be obtained, It is shown that the text ure energy method can be understood as the equivalent of an envelope d etector receiver commonly used in AM communication techniques. Feature images provided by the texture energy method are compared with their counterparts resulting from the quadrature filter approach, and criter ia helping to decide when to use which one of the methods are given.