Every so often I come across some software that, as far as I am concerned, has been hiding in plain sight. Such a program is PhotoDemon.
PhotoDemon is developed by Tanner Helland.
It was first released in 2012. It is open source and freeware, although donations can be made to the project. At the time of writing PhotoDemon is on version 2025.4.
PhotoDemon is not installed, it is an executable along with its required dependencies and requires no administrator privileges. Aside from a temporary folder – which you can specify in the Tools > Options menu – PhotoDemon leaves no trace on the hard drive. PhotoDemon can be run from a USB stick or SD card.
It is lightweight, fast, completely portable and works with 8 bit, 16 bit and 32 bit images; unlike many photo editing programs which reduce higher bit depth images to 8 bits before they can be used.
Due to its portable nature, PhotoDemon is only available as a 32-bit application. This means it cannot load or save images larger than about 2 GB in size.
Complex editing actions can be recorded as macros. A built-in batch processor lets you apply macros to entire folders of images. 32 bit 8bf plugins can be installed and used. The 32 bit 8bf, Hasta La Vista, Green, HLVG, from DeepSkyColours install and works perfectly in PhotoDemon.
PhotoDemon is very intuitive and usable. Small touches like real-time effect previews, save/load presets on all tools, unlimited Undo/Redo, customizable hotkeys, mouse wheel and X-button support, and descriptive icons make it fast and easy to use. For those who know something about Photoshop, many of the keyboard shortcuts work the same way.
PhotoDemon has very extensive file format support, including Adobe Photoshop (PSD), Corel PaintShop Pro (PSP), GIMP (XCF), and major camera RAW formats, but at the time of writing, does not support the Fits file format.
Advanced multi-layer support, including editable text layers and non-destructive layer modifications
Colour-managed workflow includes support for embedded ICC profiles.
Its on-canvas tools include digital paintbrushes, clone and pattern brushes, advanced selection tools, interactive gradients, and more.
Adjustment tools include levels, curves, HDR, shadow/highlight recovery, white balance, and many more.
Filters and effects include perspective correction, edge enhancement, noise removal, content-aware fill called ‘Heal selected area’, and resize, unsharp masking, gradient and palette mapping, and many more. More than 200 tools are provided in the current build.
Screenshot of PhotoDemon using Curves on a Star layer that has been Screen blended with the starless layer.
PhotoDemon is right up there with Photoshop, Gimp and Affinity Photo. It will be one of the tools in my workflow for processing astronomical images. I can recommend it to any astrophotographer who wishes to use a powerful yet intuitive program to contribute to the processing of her/his images.
I was unable to get it to work in Wine in Fedora or Ubuntu Linux. If it can be made to work in Wine a special Wine ‘bottle’ may have to be developed.
PhotoDemon can be downloaded from https://photodemon.org/
