nomacs est une visionneuse d'images gratuite et open source, qui prend en charge plusieurs plates-formes. Vous pouvez l'utiliser pour visualiser tous les formats d'image courants, y compris les images RAW et psd.

nomacs features semi-transparent widgets that display additional information such as thumbnails, metadata or histogram. It is able to browse images in zip or MS Office files which can be extracted to a directory. Metadata stored with the image can be displayed and you can add notes to images. A thumbnail preview of the current folder is included as well as a file explorer panel which allows switching between folders. Within a directory you can apply a file filter, so that only images are displayed whose filenames have a certain string or match a regular expression. Activating the cache allows for instantly switching between images.

nomacs includes image manipulation methods for adjusting brightness, contrast, saturation, hue, gamma, exposure. It has a pseudo color function which allows creating false color images. A unique feature of nomacs is the synchronization of multiple instances. With this feature you can easily compare images by zooming and/or panning at the exactly same position or even by overlaying them with different opacity.