Gimp 2.9 – A sneak preview of the next major version
Going Forward
The Gimp revamp is in full swing. We look at developer version 2.9.1 to explain the new components and features that are expected to find their way into the Gimp 2.10 major release.
Ever since 2.8.0 was released in 2012, rumors of the next major version, 2.10, have been rampant on the Internet. Although the project roadmap [1] doesn't name the date that Gimp 2.10 will be released, it will most likely rely completely on the new Generic Graphics Library (GEGL) [2], which supports higher bit depth images than Gimp currently supports and non-destructive editing.
With non-destructive editing, the GEGL function preview is always shown directly in the image window – a huge advantage, considering the tiny partial preview windows offered in current plugins. Editing with the library functions is always graph-based [3]: Although this might seem complicated at first sight, it offers exceptional advantages, as you will see.
In the recently published Gimp 2.8.14, you can already see the first fruits of the developers' labors. However, GEGL integration in this version does not work as well as in the developer version of Gimp 2.9: In version 2.8.14, the functions run far slower than they will in future releases. The GEGL operator under the Tools menu currently groups the features that have already been implemented (Figure 1). An icon for this tool will also appear in the Toolbox if it has been enabled in Preferences (see the box "GEGL in Gimp 2.8").
GEGL in Gimp 2.8
Your best option for testing the GEGL functions that are already implemented is to experiment in Gimp 2.8. To provide a GEGL tool in the toolbox, click on Edit | Preferences and choose Toolbox, where you can enable and disable tools and change the order in which they appear in the Toolbox palette (Figure 2). Clicking the box beside GEGL Operation adds the eye icon to indicate that the tool is enabled.
To apply the tool, you first need to click on the image in your main window then click on the GEGL tool in the Toolbox. The GEGL Operation dialog opens, where you can select a GEGL function and its corresponding parameters.
If you select a GEGL tool, a customized dialog appears in the second step that allows you to configure the function parameters. In Gimp 2.8, this is not particularly useful because you only have buffers with color depths of up to 8 bits. For HDR features, such as mantiuk06, fattal02, and reinhard05, this would be like applying the functions directly to JPEG images. Although you can be successful [4], it hardly taps into the features' true performance.
One of the GEGL operations that is already working pretty well is color-temperature correction, which recomputes the color temperature of an image. To do this, you define the color temperature of the original image and the desired color temperature: The function then converts the colors in the image accordingly. In many situations, this is your best option for applying subtle color changes or repairing a botched white balance.
Gimp 2.9
In the remaining sections of this article, I refer to the latest developer version of Gimp (Gimp Git), which is released at regular intervals. I tested on Arch Linux; all Gimp versions are numbered 2.9.1 followed by the checkout date and the revision number (e.g., 20140604.gfd928cd-1). Most of the versions in the Git master are sufficiently stable for use in smaller projects. (See the "Installing Gimp 2.9" box.)
Installing Gimp 2.9
Installing the current development version of Gimp can be accomplished in several ways. For example, you can install Gimp directly from the Git repository, although you should expect some errors. For Debian-based systems such as Ubuntu, a script automates this process [5].
For a frustration-free install, you can wait for snapshots (which are functional, for the most part), such as those regularly published in the Arch Linux repositories. You can easily install these with the package manager, but you must make sure to update your GEGL and BABL packages beforehand:
# yaourt babl # yaourt gegl # yaourt gimp-git
For Ubuntu, PPAs provide snapshots of the Git version at more or less regular intervals [6].
Not every function of the Git version is already stable; thus, you should get into the habit of saving your work at regular intervals. That said, you still cannot expect trouble-free operation: Some features require the new XCF6 file format, which is not compatible with Gimp 2.8. If you attempt to open such a file in Gimp 2.8, you will see the message XCF error: unsupported XCF file version 6 found . The same thing applies to the new XZ archive format.
After launching Gimp 2.9, the first thing you will probably notice is the greatly extended toolbox (Figure 3). New icons are not yet available for all the new tools, so initially you will need to read the tool tips to avoid guesswork. The new tools currently residing in the toolbox are the Unified Transform tool, the Warp Transform tool, and the Seamless Cloning tool.
Unified Transform
The Unified Transform tool (Figure 4) is a combination of the well-known Rotate, Scale, Shear, Perspective, and Move transformation tools. Numerous "handles" let you perform different functions in a single step.
Although you can basically do this with the Perspective tool in Gimp 2.8, achieving individual transformations in a targeted way with this approach is something nobody is likely to manage in production use. The Unified Transform tool acts on layers, selections, and paths (Figure 5). In the Tool Options window, you can see in the Constrain section which action is currently being performed. Under the From pivot and Pivot sections, you can define how Gimp uses reference points in transformations.
Warp Transform
The Warp Transform is based on the IWarp tool, which is found under the Filter | Distorts menu. Contrary to what you might expect, it has nothing to do with envelope transformation; instead, the tool is used to distort layer content in totally different ways (e.g., stretch, compress, bend, enlarge sections, etc.).
The legacy IWarp tool only provides a very small, moderately useful preview. In the Warp transformation, on the other hand, you work directly in the image window and scale the view for perfect insight into what is going on (Figure 6). As a general rule, you use a tool after selecting the desired functionality in the options of the Behavior drop-down, just like a brush whose Size and Strength you define in advance. Hardness supplements these two parameters and modifies the Strength (Figure 7).
Warp Transform, however, does not let you create animations. In IWarp, you just enter the number of images for the animation in the second tab of the IWarp dialog, and the filter itself takes care of the competing images between the start and end states.
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