How to Get Started with gThumb 4.0 Alpha: A Guide to the GTK4/libadwaita Revamp

Introduction

The open-source image viewer and organizer gThumb has undergone a massive transformation. With its recent port to GTK4 and libadwaita, the application looks almost unrecognizable compared to its older GTK3 version. On top of the visual overhaul, the new alpha release (v4.0) introduces support for WEBP and PNG animations, the ability to export images in the JXL format, and a handy censor filter that lets you pixelate or blur parts of an image. If you’re excited to try these features, this guide will walk you through everything you need to do—from preparing your system to exploring the revamped interface. Let’s dive in!

What You Need

• A Linux distribution (Ubuntu, Fedora, Arch, etc.)
• Basic familiarity with the terminal (for installing packages or running commands)
• Internet connection to download the alpha build
• Optional: Flatpak support if you choose that installation method

Step-by-Step Guide

1. Download the Alpha Build
   Head over to the official gThumb website or the GitHub releases page to grab the latest alpha tarball or package for your distribution. Look for a file named something like gthumb-4.0-alpha.tar.xz or a prebuilt Flatpak. If you prefer a more automated approach, check if your distribution offers a testing repository (e.g., a PPA for Ubuntu). Once downloaded, extract the archive to a folder of your choice.
2. Install Dependencies
   The alpha requires GTK4, libadwaita, and several other libraries. If you’re compiling from source, open a terminal and install the build dependencies. For example, on Ubuntu/Debian, run:
   sudo apt install build-essential meson ninja-build libgtk-4-dev libadwaita-1-dev libwebp-dev libjxl-dev
   On Fedora: sudo dnf install gcc meson ninja-build gtk4-devel libadwaita-devel libwebp-devel libjxl-devel
   If using Flatpak, ensure flatpak is installed and then run:
   flatpak install flathub org.gnome.gThumb//beta (if available) or add the alpha repository manually.
3. Build and Run (Source Method)
   Navigate to the extracted folder. Create a build directory:
   cd gthumb-4.0-alpha && mkdir build && cd build
   Configure with Meson:
   meson setup ..
   Compile:
   ninja
   Install locally (no root needed):
   ninja install --prefix ~/.local
   Launch gThumb from the terminal: ~/.local/bin/gthumb or find it in your application menu. For Flatpak, simply run flatpak run org.gnome.gThumb.
4. Explore the New Interface
   Once gThumb opens, you’ll immediately notice the modern, sleek look brought by GTK4 and libadwaita. The toolbar, sidebar, and status bar have been redesigned with rounded corners, softer colors, and adaptive spacing. Play around with the window resizing to see how the interface adjusts—this is a hallmark of libadwaita’s responsive design. Don’t worry if things feel different; the core functionality remains, just presented in a cleaner way.
5. Test New File Support
   Open a WEBP image or a PNG animation (e.g., a PNG with APNG frames). Navigate via File > Open or drag and drop. You should see the animation play in the viewer. To export an image in JXL format, go to File > Export As and select “JPEG XL” from the dropdown. The alpha also supports opening JXL files natively.
6. Use the Censor Filter
   Open any image, then click on Tools > Censor. A new toolbar will appear with options to choose between pixelation and blur. Drag over the area you want to hide. Adjust the intensity with the slider. This is perfect for anonymizing faces, license plates, or sensitive details before sharing.
7. Provide Feedback
   As an alpha release, you may encounter bugs or missing features. The developers encourage you to report issues on the GitHub issues tracker or the official gThumb mailing list. Your input helps shape the final stable release.

Tips and Conclusion

• Backup your images before testing the alpha, especially if you use gThumb to manage your library. Alpha builds can sometimes corrupt data.
• If the interface feels too different, remember that you can customize the layout via View > Toolbar and Edit > Preferences.
• For better performance, ensure your graphics drivers are up to date—GTK4 benefits from GPU acceleration.
• Explore the new export dialog in Step 5; the JXL format offers excellent compression without loss of quality.
• If you prefer the old look, you can still use the stable GTK3 version alongside this alpha—just install them in separate prefixes.

GThumb 4.0 marks an exciting step forward for this long-standing application. With its fresh coat of paint and modern file format support, it’s ready to compete with proprietary image viewers. Give the alpha a try, and you’ll see why the developers say it’s “barely recognisable.” Happy testing!