Daniel Sage · Center for Imaging and Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL)
AUGUST 2026
OrientationJ is open-source software for the directional analysis of 2D images: a series of Java plugins, easy to install on ImageJ and Fiji, free under the GPL-3.0 licence — how to cite. It relies on the gradient structure tensor, evaluated over a small window at every pixel, from which it computes the directional features that say how the local structure is organized: its orientation, the coherency telling whether that orientation is well defined, and how anisotropic the neighborhood is. One parameter controls the measurement, the analysis scale σ, the size of that window.
OrientationJ holds several plugins: Analysis for the feature maps and the color survey, Distribution for the angular histogram, Vector Field for the overlay, and MonogenicJ for a multiresolution analysis. Every command runs from a dialog and from an ImageJ macro. In addition, 16 test images come with the documentation, together with the assessments built on them: the angular distribution against other tools, the accuracy of the five gradients, two Python implementations of the same tensor — a faithful port and a minimal operator — and the structure tensor against the nematic tensor.
Fibers, filaments, fringes, cracks, fractures, flows, growth rings: many scientific images are made of elongated structures, and what matters about them is their direction. OrientationJ quantifies that direction everywhere in the image, and more than 300 published studies have used it to do so — from the actin cytoskeleton to nanofibers and bone.
OrientationJ measures orientation in 2D images only. For volumes, the EPFL Center for Imaging develops OrientationPy, its Python successor: the same gradient structure tensor, in 2D and in 3D, usable as a library or through its napari plugin.
On ImageJ — download OrientationJ_.jar (version 2.2.0), copy it into the plugins folder, restart. On Fiji — Help ▸ Update… ▸ Manage update sites, tick BIG-EPFL, apply and restart; Fiji then keeps the plugin up to date by itself. Either way the commands appear under Plugins ▸ OrientationJ. Both routes, with the older versions and the build from source: installation.
Installation · How to use · How to cite · Theory · Test images · Assessments · Use cases · Javadoc API
The original OrientationJ website remains at bigwww.epfl.ch/demo/orientation.
Collagen fibers on the left, the same field as a color survey on the right: hue gives the orientation, saturation the coherency. How that image is built, and how to read it: Color Survey HSB.
Z. Püspöki, M. Storath, D. Sage, M. Unser, Transforms and Operators for Directional Bioimage Analysis: A Survey, Advances in Anatomy, Embryology and Cell Biology, vol. 219, Focus on Bio-Image Informatics, Springer, 2016.
Three further references cover the angular distribution, the local measurements and the monogenic analysis, each with its PDF and BibTeX: how to cite.
OrientationJ is free and open-source software, distributed under the GNU General Public License v3.0, and provided as is, without warranty of any kind. If it contributes to work you publish, we expect a citation or an acknowledgement.