Image processor

Darktable 2.2.0

Darktable is a photo management and processing tool that's good enough for professional use and can even replace costly proprietary alternatives like Adobe Lightroom. It's brilliant because it allows you to split the tasks of importing, processing, and rendering photos into logical steps, and it provides a lot of cutting edge tools to help you. The color processing, exposure adjustments, lens correction, and sharpening tools are essential, for example, and have often compensated for my very poor photography skill, even when those photographs are destined for print.

This is a major release with lots of major new features – there have been more than 2,000 commits to the project's repository since version 2.0, for instance. But, if you play with only one new feature, is has to be the perspective tool. Ever since the days of Deluxe Paint, there's been nothing more satisfying that transforming a two-dimensional map of pixels through three-dimensional space. Rather than remapping pixels across a simple polygon, however, Darktable allows you to compensate for perspective distortion effects, letting you adjust the vertical and horizontal lens shift, for example, as well as shear and rotation within this 3D transformation. But – and this is the clever part – it does this by first analyzing your photo for structural features within the image itself, looking for parallel linear elements to use as anchors for the transformations. These create converging lines to a vantage point, which is then used to calculate the perspective and how the image should be transformed. The results are natural and brilliant. You can make walls vertical, for example, and you can shear the image around one of the diagonal lines within the image. Perfect if you don't have a quadcopter handy.

Another new tool is liquify. This groups together a series of other tools into one easily controllable effect. The effect is controlled by drawing a point, a line or a curve onto your image, and the way each affects the pixels is slightly different but generally looks like the image is printed onto a moving piece of material. It's great for working with text, for example, by warping its shape. Our next favorite new module changes the colors within an image by swapping them with colors held in a table. It's called the "color checker lut module," with "lut" meaning look up table. A simple lookup table is how some of the color rendition presets work, swapping out one palette for a new one and replacing one set of colors with another, but with the new plugin you can now create your own replacement palette or adjust others to nail the effect you're looking for, rather than relying on presets.

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