AstroThumbs 1.2.0

Thumbnails for XISF and FITS files in your Linux file manager.

1. What AstroThumbs does

AstroThumbs draws your astronomical images as thumbnails in the file manager, so a folder of subframes looks like the pictures it contains instead of a wall of identical icons.

Thumbnails: every .xisf, .fits, .fit, .fts and .dpproj file shows a rendered preview of the frame.
A stretch that matches what you expect to see: linear astronomical data is almost black on screen. AstroThumbs applies the same kind of screen transfer function PixInsight uses, so the frame looks the way it does in your processing software rather than the way it sits on disk.
Stars survive being made small: stars are two or three pixels across. A plain average erases them, so the downsample keeps the brightest value in each cell as well as the average and blends the two.

It reads the file directly. It does not require PixInsight, CFITSIO or any other software, and it makes no network connection of any kind.

What is not included on Linux

The Windows version also provides a preview pane and sortable metadata columns in Explorer. Neither exists here, and that is a limit of the desktop rather than a missing feature:

No preview pane. GNOME Files has never had one, and its space-bar previewer uses its own renderers with no way to add a format. On KDE, the Dolphin information panel already shows the AstroThumbs thumbnail at a usable size, which is the closest equivalent and needs no setup.
No metadata columns. Nautilus has no mechanism for adding columns. On KDE they would require a separate KFileMetaData plugin, which is not part of this release.
No process icon or sequence files. The Windows version reads PixInsight .xpsm process icons and Siril .seq sequences, which hold no image: everything they offer is a text listing in the preview pane, and the two surfaces above are the ones Linux does not have. Those files are left to the programs that own them here, and the Linux packages do not claim their file types.

For a closer look at a frame in GNOME Files, increase the icon zoom. AstroThumbs renders up to 1024 pixels, so the largest zoom level shows real detail.

2. Installation

Two packages. The first is the product; the second is optional and adds a window for entering your license key.

On Debian, Ubuntu, Mint and derivatives:

sudo apt install ./astrothumbs_1.2.0_amd64.deb ./astrothumbs-settings_1.2.0_amd64.deb

On Fedora, RHEL, openSUSE and derivatives:

sudo dnf install ./astrothumbs-1.2.0.x86_64.rpm ./astrothumbs-settings-1.2.0.x86_64.rpm

On arm64 the file names end in arm64.deb and aarch64.rpm instead.

Then restart your file manager so it picks up the new file types. On GNOME:

nautilus -q

If you skip astrothumbs-settings, everything still works: the astrothumbs-license command does the same job from a terminal. The separate package exists so that a machine with no desktop does not have to install GTK.

Supported desktops

AstroThumbs installs a standard freedesktop thumbnailer, so it works in every file manager that follows that standard:

GNOME (Files), and desktops built on it such as Budgie
KDE Plasma 6 (Dolphin)
Cinnamon (Nemo), MATE (Caja), XFCE (Thunar)
LXQt (PCManFM-Qt) and LXDE (PCManFM)

KDE needs Plasma 6. Support for third-party thumbnailers arrived in KDE Frameworks 6.6, released in September 2024. Earlier KDE versions, including those in Kubuntu 24.04 LTS and Debian 12, ignore them entirely, so nothing will appear and nothing will explain why. The rest of the desktops above have no such requirement.

A file manager installed as a Flatpak or Snap runs in its own sandbox and cannot see thumbnailers installed on the system, so use your distribution's own package.

Requirements

glibc 2.34 or newer, which covers Ubuntu 22.04, Debian 12, RHEL 9 and anything more recent. Two architectures are provided:

x86-64, for any 64-bit Intel or AMD machine. Packages are named amd64 on Debian and Ubuntu, x86_64 on Fedora and RHEL. Those are two names for the same thing.
arm64, for a Raspberry Pi 4 or 5 running a 64-bit system, and for other ARM machines. Packages are named arm64 or aarch64, again two names for one architecture.

If you are unsure which you have, run uname -m: x86_64 means the first, aarch64 the second.

3. The AstroThumbs window

Open AstroThumbs from your applications menu. It shows whether this machine is in trial or licensed, how many trial days remain, and lets you enter a license key.

The same information from a terminal:

astrothumbs-license --status

Refreshing thumbnails

Your file manager remembers thumbnails, including failures. If files still show blank or generic icons after you activate a license, that memory is what you are looking at. Use Clear thumbnail cache in the window, or:

astrothumbs-license --clear-thumb-cache

Then close and reopen the file manager.

Rendering

Four settings, matching the Windows version:

Auto-stretch images. On by default. Turning it off shows the raw linear data, which for most astronomical frames is almost black.
Brightness. How light the background is rendered: darker, standard or brighter. Standard is the value PixInsight uses.
Mosaic images. Whether a one-shot-colour frame is rendered in colour from its Bayer data, always in mono, or decided automatically. Automatic renders colour except for calibration frames, where colour means nothing.
Show the format on the thumbnail. Off by default. Draws a small XISF, FITS or DP badge in a corner of the picture, so an astronomical file is distinguishable at a glance from an ordinary JPEG or PNG once every file in the folder shows a picture.

These settings apply to every account on the computer, and changing them asks for your password once. That is not a design choice: GNOME runs the thumbnailer in a sandbox that cannot read your home folder, so a per-account setting would silently do nothing on the most common desktop.

Changing a setting does not redraw thumbnails your file manager has already cached. Use Clear thumbnail cache to see the change on existing files.

From a terminal:

astrothumbs-license --prefs
sudo astrothumbs-license --set labelformat=on brightness=brighter

The stretch algorithm itself, the star-preserving downsample and the four-second decode budget are fixed at the values the product was tuned for. On a slow or networked drive a large frame may take a moment the first time and is instant afterwards, because the result is cached by the desktop.

4. Trial and licensing

AstroThumbs runs fully functional for 15 days. Nothing is watermarked or reduced during the trial. When it ends, thumbnails stop being generated and your files show their normal icons again.

To activate, open the AstroThumbs window, enter the e-mail address you bought with and the key from your activation message, and click Apply license. Or from a terminal:

astrothumbs-license --register you@example.com YOUR-KEY-HERE

One license covers all your computers and all platforms. The same key activates AstroThumbs on Windows, macOS and Linux. You activate each computer once.

GNOME needs one extra step

GNOME runs thumbnail programs inside a sandbox that cannot see your home folder. Your license lives there, so GNOME cannot read it until it has been copied to a system-wide location. You will be asked for your password once when you activate. Please say yes: without this step your license is stored correctly but your thumbnails stay blank.

If you declined, or activated from a terminal that could not ask, run:

sudo astrothumbs-license --enable-gnome

KDE, XFCE, Cinnamon and MATE do not sandbox thumbnailers and need nothing extra.

To check that GNOME can see your license, look at the GNOME line in astrothumbs-license --status. It should say licensed, visible to the thumbnail sandbox. If it says your license is not copied yet, thumbnails will keep working until the trial ends and then stop, so it is worth fixing when you see it rather than later.

DeepParallax Studio owners

A DeepParallax Studio license also entitles you to AstroThumbs. Nothing needs entering: it is detected automatically. On GNOME, run sudo astrothumbs-license --enable-gnome once so the sandbox can see it.

5. Troubleshooting

No thumbnails at all

Check that the file type is recognised:

xdg-mime query filetype yourfile.xisf

It should print image/x-xisf, or application/fits for FITS files. If it prints something else, the MIME database has not been refreshed; log out and back in.

Then try the thumbnailer directly, which prints the reason for any failure:

astrothumbs-thumbnailer -s 256 yourfile.xisf /tmp/test.png

Thumbnails stopped working

Almost always the trial ending. Run astrothumbs-license --status. If it says Expired, entering a license restores them. If it says Licensed but the GNOME line does not, see section 4.

No thumbnails on a network drive, in Dolphin

KDE does not generate previews for files it considers remote, and that includes anything on a mounted network share such as Samba, NFS or a NAS. The limit is off by default, so nothing appears and nothing explains why. This is a KDE setting rather than something AstroThumbs controls.

In Dolphin, go to Settings > Configure Dolphin > Interface > Previews and raise Skip previews for remote files above to a size that covers your frames. From a terminal, the equivalent is:

kwriteconfig6 --file dolphinrc --group PreviewSettings --key MaximumRemoteSize 52428800

That sets the limit to 50 MB. GNOME Files has no such limit, which is why the same files show thumbnails there and not in Dolphin.

Some files show icons, others show pictures

Files the decoder cannot read keep their normal icon, which is deliberate. A .fit file from a Garmin device is the common case: that extension is shared with fitness activity files, and AstroThumbs checks the contents rather than trusting the name.

Where things are kept

astrothumbs-license --paths

6. Contact

Questions, bug reports and feature requests are welcome at deepskycolors.com.