Analysis of bulk fabrics and microstructure variations using tesselations of autocorrelation functions

Lazy ACF Tiles, a macro written for the public domain program "NIH Image", is presented. The macro permits the user to calculate local and bulk autocorrelation functions (ACFs) of halftone images such as photomicrographs of geological thin sections. Single ACFs, row's. or tessellations of ACFs can be calculated. ACF analysis is especially useful for the detection of subtle microstructures (weak anisotropies), and for the evaluation of large data sets. Segmentation of images (grain boundary contouring) is not necessary. Images do not have to be square. The macro is in the public domain and a powerpoint manual is provided with it. As an example, the application of "Lazy ACF Tiles" to an experimentally deformed sample of quartzite is demonstrated, The ACF analysis reveals a periodic flattening intensity along the compressional axis of the sample, which cannot be detected with the unaided eye. (C) 2002 Elsevier Science Ltd. All rights reserved.