The wait is over. After several years of work, the Gimp development team has unleashed version 3 of the premier open source image editing application. Gimp 3 [1] mixes changes under the hood with new features that improve both the workflow and capabilities of the program.

Headlining this release, more of Gimp's features now fit within a non-destructive approach. In other words, you can make changes to an image without committing to them. This includes images that have been saved and then reloaded in Gimp's native XCF format, which means that you retain full editability and can back out of changes at any time, a boon both for individual users and collaborative teams.

Beyond this, nearly every area of the program has a few new features to offer. Read on for an overview of the improvements.

Checking It Out

Gimp 3 has replaced Gimp 2 in the repositories of the major Linux distributions such as Ubuntu. It's also in the Flatpak and Snap repositories, but bear in mind that using these repositories may cause some extra hunting to find various internal Gimp folders if you intend to add extensions and custom scripts. Improvement in the management of add-ons is planned for later 3.x releases.

The user interface is the first point of contact for the user, and this now benefits from an improved Welcome dialog. It's worth spending a bit of time here to scale the user interface to your liking (in the Personalize tab), and it helps that your choices are reflected in real time. In my case, I scaled things up in the areas of font and icon size and selected the Legacy (color) icon set (Figure 1). You can get back to this dialog, later, via the Help menu once you've dismissed it.

Figure 1: I chose large color icons in the new Welcome dialog.

Gimp has now transitioned from the GTK2 toolkit to the more modern GTK3. It's ironic that the user interface has been through some of the biggest changes in the code, and yet at first glance, the application doesn't look much different from Gimp 2.x. However, the more you use Gimp 3, the more you will notice small user interface improvements, and it's reassuring to know that this aspect of the program is running on top of a modernized, forward-looking base.

GTK3 brings with it Wayland support and better HiDPI support for those with a high resolution monitor. The use of CSS to define the interface layout and color scheme has the potential to provide many benefits. Even users who don't want to tweak the CSS themselves can look forward to the inevitable collection of downloadable layout customizations that are sure to appear.

Non-Destructive Editing

Non-destructive editing is the area with most user-facing improvements in Gimp  3. Frankly, its absence until now has meant that Gimp was starting to fall behind some of the competition. In Gimp 3, non-destructive editing is not a single feature; instead, it's an approach that much of the program now adheres to.

To give an example, say you want to edit a photo in Gimp and increase the brightness. As in previous versions of the application, you would open the appropriate menu entry (Colors | Brightness – Contrast…) and adjust the Brightness slider. As before, the brightness changes are reflected in real time, and you can click on OK when you're happy with the results.

The difference is that Gimp 3 now regards this as what it terms a "layer effect." If you examine the Layers panel (on the right-hand side of the window, by default) there is now an entry on the fx column (Figure 2). Clicking on this opens the Layer Effect dialog, which shows a single entry, Brightness-Contrast. Sure enough, if you click on the eye icon next to this entry, the adjustment you've just made to the image is removed. Then you can click on it again to see the effect reapplied. Double-click on an entry to reopen its dialog to change the settings.

Figure 2: The Layers panel now has an fx column for non-destructive effects.

Nearly all of the effects and filters now work in this way and can be deleted or readjusted at any stage. Gimp 3 transparently carries out all of the work to create layers and keep notes of what changes were made. On previous versions, if you realized that you had made a mistake earlier, you'd have three options: live with the mistake, try to adjust the image to compensate, or simply start from scratch.

Each effect change that you apply to the image is added to a stack in the Layers menu, and you can double-click on it to reopen its dialog to make tweaks at any time. The stacking also means that you can remove an effect or change the order of effects (Figure 3). Many of Gimp's effects produce considerably different results depending on their order, making this feature a godsend for experiments. It couldn't be more flexible.

Figure 3: Layer effects can be listed, reordered, edited, or deleted.

Passing It Around

Layer effects are even more useful because they are saved when you use Gimp's native XCF file format, meaning that they are preserved between work sessions. They are even preserved when you share a file with someone else, allowing the other person to adjust the effects as well. As one would expect, the other person's computer must have the same filters installed. So, make a note of any effects you've used that aren't part of the standard Gimp installation when passing the file on to someone else.

One thing to consider about non-destructive editing is that it inevitably causes some overheads. Using a medium-level machine, I did notice some slight slowdowns when I really started to pile on the effects. For the same reason, memory usage is slightly increased as layers are being transparently created by Gimp. However, on most modern computers with 8GB of RAM or more, this has a negligible impact. If you do want to opt out of using non-destructive editing, most dialogs now include a Merge filter checkbox (Figure 4), which causes the program to apply the effect, permanently, in the same manner as Gimp 2, eliminating the increased resource usage. However, when evaluating the overheads of non-destructive editing, take into account the amount of time you'll save due to keeping the layer effect chain fully editable at every stage.

Figure 4: Click Merge filter in a dialog to impose the old, destructive style of editing.

It's also worth noting that not every part of the program uses non-destructive editing at this stage of development. For example, if you crop an image, this can't be undone later. The same can be said if you start painting on the canvas with a brush. In both cases, you can work around this by manually creating a new layer, just like in previous versions. Perhaps, in a later 3.x release, even more of the program will be non-destructive by default. On the plus side, if you cut and paste an area, it is now automatically added to its own layer, which keeps things editable.