  The last 15 years have seen a surge of new multi-chip optical and near-IR
imagers. While some of them are accompanied by specific reduction pipelines,
user-friendly and generic reduction tools are uncommon. In this paper I
introduce THELI, an easy-to-use graphical interface driving an end-to-end
pipeline for the reduction of any optical, near-IR and mid-IR imaging data. The
advantages of THELI when compared to other approaches are highlighted.
Combining a multitude of processing algorithms and third party software, THELI
provides researchers with a single, homogeneous tool. A short learning curve
ensures quick success for new and more experienced observers alike. All tasks
are largely automated, while at the same time a high level of flexibility and
alternative reduction schemes ensure that widely different scientific
requirements can be met. Over 90 optical and infrared instruments at
observatories world-wide are pre-configured, while more can be added by the
user. The online Appendices contain three walk-through examples using public
data (optical, near-IR and mid-IR). Additional extensive online documentation
is available for training and troubleshooting.
