December 15, 2005

Review: Pixel image editor

Author: Nathan Willis

Looking for an Adobe Photoshop replacement on Linux? If the GIMP doesn't cut it, maybe Pixel will.

Pixel is a raster image editing program that runs on more than a dozen operating systems, including Windows, Mac OS X, and Linux on i386, AMD64, and PowerPC.

Pixel's feature set rivals that of Adobe Photoshop and outstrips the GIMP in several key areas. Pixel supports CMYK and Lab color modes, 16- and 32-bit color depth, and chic new features such as adjustment layers. The application is low-cost but not free, with revenue supporting its creator and lone developer Pavel Kanzelsberger.

Kanzelsberger has been writing Pixel in his spare time -- and by himself -- for the past eight years. In a few months, he says he will officially release Pixel 1.0, quit his current job, and work on Pixel full-time. The first version of Pixel was written for DOS in 1997, and a version for Windows followed in response to user requests. Be then contracted Kanzelsberger to port the application to BeOS.

To mitigate the complexity of maintaining multiple OS builds, Kanzelsberger wrote an SDL-based toolkit called eLiquid, and rewrote Pixel using it. This design enables Pixel to run on more than a dozen operating systems today. Windows accounts for just over half the licensed downloads, but Linux comes in second.

Running Pixel

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A 30-day, watermarking demo is available on all supported Linux platforms. Both the demo and the full version depend on Freetype, LittleCMS, SDL, and the JasPer JPEG2000 library. Pixel's usage of Freetype and LittleCMS lets it integrate seamlessly with the user's system-wide font and color management installations.

Pixel uses the multiple document interface model familiar to Photoshop users and presents similarly laid out toolboxes and menus. In fact, only minor differences distinguish Pixel's interface from that of its more expensive rival -- filters are called "Effects" for example, and the menus are in a different order. But anyone used to Adobe's interfaces will have a smooth transition -- the same visual metaphors for tools, the same terminology for operations and options, and most of the same keybindings.

My only complaints with the interface are that several of the tool icons are too similar in appearance (slice, brush, airbrush, and eraser) and the low contrast of the toolboxes sometimes require a moment's distraction to ensure that I've selected the right tool or option. Pixel is by no means alone in this regard; it is common in graphics applications to have so many tools and buttons that you run out of distinct shapes that are visible at tiny dimensions.

Pixel supports grayscale, RGB, CMYK, and CIE Lab color modes at 8-bit, 16-bit, and 32-bit color depths. Color management is available for all file types that support it. The image adjustment tools include the standard fare, such as levels, curves, and color balance, plus some bonuses like gamma adjustment, tone, and exposure control -- welcome additions for those used to working in the GIMP. TWAIN-compatible scanners are supported, as are pressure-sensitive tablets -- though not yet on all platforms.

Among the advanced editing features are both "adjustment" and "live effects" layers: image layers that modify all the content on underlying layers (to create drop shadows or make curve corrections, for example), but which can be turned on or off without altering the content of these other layers. Layer masks, transforms, channel splitting and combining, and some path operations are available. There is also a top-level Animation menu for creating basic animated images.

Kanzelsberger takes feature suggestions from his users seriously. One large group of Pixel users consists of Windows graphics artists looking to transition to Linux; it was their insistence that led to CMYK and color management. Indeed, many of the common complaints about the GIMP are answered in Pixel, including the aforementioned CMYK support and high-dynamic-range image editing.


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The current release of Pixel is Beta 6, and there is still some unimplemented functionality. Not all effects are available for all color models and bit depths, some menu items are greyed out in the build that I tested (including, regrettably, the built-in bug report tool), some TIFF compression is unsupported, and tablet support is still forthcoming for Linux.

Kanzelsberger says he regards the current feature set as frozen, and assures customers that all of these holes will be filled by the 1.0 release. Expansion of the feature set -- such as "natural media" effects and vector operations -- are earmarked for the 2.0 branch.

Experienced Photoshop users will miss certain features in Pixel. Pixel ships with just over 100 filters and effects; a subset of the more expensive program's offering, but -- as is analogous to the free-versus-Microsoft office suites situation -- the most useful subset.

The selection tools are also more modest; I missed the ability to expand or contract selections, which is present in Photoshop. Text tool operations are solid, but don't expect anything fancy, such as fitting text to a path. If you can do without these specific functions, however, Pixel may be just what you are looking for.

Exempting the disabled features, Pixel performs admirably on Linux. Effects and adjustment tools are full-featured, permitting precise keyboard-input parameter tweaking and the loading and saving of presets.

In one week of testing I experienced only one crash, which I was unable to reproduce. It occurred when working with a Lab color image. Pixel had no trouble opening 50-100MB image files, sizes that routinely segfault the GIMP.

Pixel and open source

Pixel is neither free nor open source. A license purchased now (during the beta phase) costs $32, but will remain good for all updates up to and including Pixel 2.0, and can be used for all available platforms simultaneously. After Kanzelsberger completes Pixel 1.0, however, the price for a license will go up to $100.

Kanzelsberger is by no means against open source, though; he is a Gentoo Linux user and Pixel links against several free libraries. He simply charges for Pixel as a means of supporting himself and continuing its development.

For the most part, Kanzelsberger says, Linux users have been positive in their comments on his work. There is the occasional gripe that he should release the project for free, but most welcome the alternative to expensive graphics suites from Adobe and Macromedia.

Kanzelsberger has expressed willingness to open source the eLiquid GUI toolkit in response to a growing number of programmers' requests. After all, it is fast, lightweight, and runs on a dozen operating systems. An eLiquid release definitely won't happen until after Pixel 1.0, though, as he wants to focus on completing his main project, and organizing and documenting the eLiquid code base will take time.

Wrap up

There is very little in the way of consumer-priced commercial software for Linux, particularly in the graphics arena. There are studio-level 3D and compositing applications bearing four- and five-digit price tags, but almost nothing in wallet range for the individual.

For photo editing and raster graphics, many users see running Photoshop under WINE as the only choice for tasks they can't handle with the GIMP. Certainly, if you already own a copy of Photoshop or one of the expensive bundles that include it, it is a reasonable option. But if you don't, you will find 90% of what you need running natively on Linux at a fraction of the cost by switching to Pixel.

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