MAVI - modular algorithms for volume images. MAVI focuses on the characterization of the complex geometry of microstructures. Volume, surface, integrals of curvature and Euler number are determined for the whole structure or isolated objects. Anisotropies and preferred directions are not only found but their strength is measured, too. This core is complemented by various filters and transforms, techniques for image segmentation and object isolation, and functions for easy handling of huge image data sets. For special applications, several analysis tools are combined into user friendly modules with few parameters and formatted output. MAVI provides local analysis methods, e.g. for local porosity, thickness or orientation analysis. For fiber reinforced composites, local fiber orientation tensors can be measured.