ON TEXTURE ANALYSIS - LOCAL ENERGY TRANSFORMS VERSUS QUADRATURE FILTERS

The well-known method proposed by Laws for texture analysis first subjects the texture to a filter bank, followed by the computation of energy measures, e.g. through local variance estimation. As shown by Unser in 1986, the filter bank application is equivalent to a linear transformation of the grey values of neighbouring pixels. In this contribution, we derive a further linear relationship between the local variances of the filter outputs and the autocorrelation function of the texture process. Furthermore, we examine how the filter bank approach is related 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 texture energy method can be understood as the equivalent of an envelope detector 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 criteria helping to decide when to use which one of the methods are given.