Lightning Image Viewer is fast and lightweight desktop image viewer featuring minimalistic "transparent fullscreen overlay" UI/UX with controls similar to map apps. It is free (as in FOSS, licensed under GPLv3) native (as in native code) cross-platform app (written in C with SDL3, tested on Linux and Windows). Detailed description and source code are available on GitHub. This webpage is primarily demo featuring actual app which is compiled to WebAssembly and runs in browser via Emscripten. It is launched after image file is selected and renders to canvas, displaying image over webpage content just like native build displays over desktop and handling input events same as native. It should work in all mainstream browsers.

Image file:

Controls:

• mouse scroll up/down: zoom in/out, preserving image point currently under mouse cursor
• keyboard =/-/0: zoom in/out/1:1, preserving image point currently in the center of the screen
• mouse move with left button pressed: pan
• keyboard Up/Down/Left/Right: pan up/down/left/right
• mouse middle button click || keyboard F, F11: toggle fullscreen
• mouse left button click with no move nor zoom between button press and release || keyboard Esc, Q, Enter: close
• keyboard R/L: rotate 90deg clockwise/counter clockwise
• keyboard M: mirror horizontally
• keyboard PgDn/PgUp: prev/next image app running in browser cannot access local filesystem, so this only resets view of opened image

Downloads: check GitHub releases

Feedback: check GitHub issues

Known issues specific to this demo webpage:

• image formats support is limited to formats internally supported by SDL3_image library (BMP, GIF, JPEG, LBM, PCX, PNG, PNM (PPM/PGM/PBM), QOI, TGA, XCF, XPM, and simple SVG format images) (because I didn't bother to build external dependencies needed for AVIF, JPEG-XL, TIFF, and WebP)

Special thanks to:

• JYKITORS, for constantly supplying me with free (as in beer, not as in speech) delicious sushi (not as in Sushi file previewer for GNOME/Nautilus; by the way, this viewer can be used like Sushi/QuickLook, toggling (pre)view with Enter key, given that your file manager is configured to open images with it upon Enter key press; or with any other key, if you can configure your file manager accordingly and build the viewer with patched source to bind the key to exit action; check the event loop in main())
• ChatGPT (in case it does have consciousness after all), for its time-saving advice, and all humans who created knowledge which it was trained on
• all conscious humans who don't copypaste valuable lossy-compressed images as pixmaps (which causes loss of compression and addition of new compression artifacts upon repeated lossy compression) but share them as files

Built from commit 667415578e824a8ebe09e6ed826bbaab1d35c5f3 with tag v0.3.0