nomacs vs Okular

nomacs is a free, open-source image viewer for Windows, Linux and macOS, with support for common formats including RAW and PSD. It provides semi-transparent panels for thumbnails, metadata and histograms, and lets users attach notes to images. File browsing includes images within ZIP and MS Office files, folder thumbnail previews, and filename filters based on text or regular expressions. Image adjustments include brightness, contrast, saturation, hue, gamma and exposure, along with pseudo-color rendering. For comparison, separate nomacs instances can synchronize panning and zooming, and images can be layered at different opacity. The project also lists FreeBSD and OS/2 as supported systems. Available downloads include Windows installer and portable packages, Linux packages and Flatpak or AppImage, and macOS builds for arm64 and x86_64. Format availability depends partly on Qt image plugins, KImageFormats and optional build features, so support may differ between builds. The GNU General Public License v3 permits private and commercial use.

Okular has no write-up on Specifiction yet; its figures are above.