The best thing about Linux is the great variety of available free tools – whatever it is you need to do, the open source community has at least one – and probably several – tools for the task. Raster graphics is no exception. The famous Gimp (Gnu Image Processor) is the highest profile graphics tool in the Linux space. Gimp ships with many popular distros, and the ones that don't include Gimp by default make it available through package repositories. Many users adore Gimp, but it isn't for everybody. Some users think Gimp is too big and confusing, with too many different features. Others prefer a tool that is targeted to a more narrow set of tasks.

Another free tool in the raster graphics space is Pixelitor, an open source graphics editor based on Java. Pixelitor [1] is truly a cross-platform application that caters to users on Mac OS and Windows as well as Linux. Pixelitor supports "layers, layer masks, text layers, filters, and multiple undo." The latest version ships with more than 110 filters and color adjustments (such as the Photo Collage filter shown in Figure 1). But beginners beware: the project developers make it clear that Pixelitor is "… intended to be powerful rather than simple. You should have some experience with image editors in order to use it, because there isn't much documentation available yet, [although] many concepts (layers, blending modes, cropping, Gaussian blurring, unsharp masking, histograms, etc.) are the same" as with other similar tools. Pixelitor doesn't provide a lot of hand-holding for beginners, but many converts believe it offers a more compact and streamlined interface for users who know what they are doing.

Figure 1: Pixelitor's Photo Collage filter creates a collage from a single image.

We decided it was time to take a closer look at Pixelitor and the capabilities it brings to the Linux space. But I'll start with a note on formats. Pixelitor uses the PXC file format as its native format, which should not be confused with the Picture Exchange (PCX) format [2] used with Gimp and other tools. Pixelitor can export files into the usual export formats, such as JPEG, PNG, BMP, and GIF (without transparency), but the Pixelitor developers recommend using PXC to save all internal information, such as layers, selections, and paths, and other elements.

If you wish to save layers and open the file somewhere else, like in Gimp or Krita, OpenRaster (.ora extension) is the better choice as an export format. OpenRaster format will preserve the layers, although it will not retain layer masks and other enhanced features.

The other important note is that Pixelitor currently only supports a color depth of 8 bits, which was considered sufficient for PC-based applications in years past but is definitely not up to the quality of today's high-quality professional tools.

Getting Started

See the box entitled "Installation" for first steps to install PixelitorAfter launching, the program shows a tip to help you use the software. You can load an image from the File menu or by dragging it onto the window with the mouse. Additionally, the program supports pasting from the clipboard (Ctrl+V).

java -jar Pixelitor.jar

Tools work in Pixelitor as in Gimp: Exactly one tool is active at any given time. Filters and other functions can be used in parallel, but this does not affect the tool. The software is limited to a set of essential tools, which it offers in the toolbar on the left (Figure 2). Compared to Gimp, the tools are more generic and have significantly fewer settings.

Figure 2: The tools in Pixelitor reside in a toolbar on the left side of the window.

The application has a Move Tool at the top that only worked on layers in our lab, so I cannot say whether and how moving selections or paths works. During cropping, you can find guidelines under the Guides drop-down, much as Gimp offers for various aspect ratios.

A universal Brush Tool is available for drawing and painting. Different brush tips simulate various tools, such as an airbrush and a calligraphy pen. Only a few of the tips support settings (Figure 3), which means tools that otherwise work well are difficult to adjust or adapt. The brush can be adjusted down to the One Pixel level.

Figure 3: Some tools allow you to adjust parameters more precisely in a Settings dialog.

Cloning (indicated by a stamp icon for the Clone Stamp Tool) is essentially a healing tool that takes the brightness values in the area into account. However, Pixelitor does not display the area from which the pixels originate nor the size of the brush tip during cloning; thus, you need to rely on your intuition to understand the scope of your actions.

The tools for erasing and smearing are similar to those for painting. The same brush tips are available for the Eraser Tool as for painting, whereas the Smudge Tool has only a hard and a soft brush for smearing. Because alpha channels are automatically added to the layers, the eraser always creates a transparency. The Smudge Tool allows you to create a virtual background color with the Finger Painting option at the top of the window. Without this option, smearing works like the basic settings for the tool of the same name in Gimp.

As expected, Pixelitor only supports one color gradient: an even gradient from foreground to background color. As with Gimp, the Gradient Tool fills the entire image if no limiting selection exists. The same applies to the Paint Bucket Tool (fill tool), which supports colors, but not patterns. The Color Picker Tool pipette works as expected: If you enable it, each mouse click changes the color for the foreground.

If required, you can also create paths as BÈzier curves, which you can adapt and later convert into a selection, if required. The Pen Tool has two modes: Build and Edit. However, you can only remove nodes you set previously in Edit mode, and you need the mouse to toggle between modes in a drop-down at the top of the window, which is annoying in daily work. In the context menu (Figure 4) of the Pen Tool, you will find the Delete Point function.

Figure 4: You can create or edit paths with the Pen Tool. Additional functions are available in the context menu.

The heart icon is the Shapes Tool for creating predefined shapes. The Effects button lets you further modify these figures; however, such gimmicks are of limited value in everyday work.

The Hand Tool moves the view, much like the Navigator in Gimp. A real navigator is also available: You will find it under View | Show Navigator. However, it will not dock. As a rule, you only need these aids if you cannot intuitively move the displayed section with the mouse. The magnifying glass is the Zoom Tool and works as you would expect.

At the bottom of the left sidebar is a color selector for the foreground and background color, with three buttons for special color settings (Reset Default Colors, Swap Colors, and Randomize Colors). As with the filters, the randomize button lets you select colors or other parameters randomly.

Selections

The Pixelitor Selection Tool is symbolized by a square ant line. Use the Type drop-down to select from four shapes, including Freehand and Polygonal. You can use the different types one after the other, although it's neither intuitive nor effective and requires good planning to achieve any results quickly.

The polygons do not have anchors, so they cannot be adjusted later. If necessary, you can combine several selections with the New Selection drop-down (Replace, Add, Subtract, Intersect), but it is much more time-consuming than Gimp's usual procedure.

Soft selection, which is a commonly used image editing operation that reduces the selection strength from 0 to 100 percent over a preset range (radius), is currently not supported by the program, limiting the ability to smooth transitions. If necessary, you can use the buttons at the top of the window to convert paths into selections. In the same way, a selection can be dragged – the brush follows the path. However, there is neither a dock to manage multiple paths, nor a selection editor, which limits your editing options to very simple tasks.

Layers

At the right edge of the Pixelitor window is an area where you can see the stack of layers; as usual, eye symbols mark their visibility. The layers always have an alpha channel, so they are always transparent and correspond to the size of the image, which might not make much sense, but at least it does not cause any problems.

Surprisingly, the program provides masks for layers that you can reach by clicking a button below the list of layers (the second icon from the right). As in Gimp, you enable the mask by clicking on it and editing it with the painting tools.

Text layers are created in Pixelitor by pressing the stylized T icon at the bottom of the layer pane (or with Filter | Text from the menubar). In the dialog that opens (Figure 5), the tool supports alignment and a number of Advanced settings (e.g., Strikethrough, Ligatures, Tracking). The Effects pane lets you add Glow, Neon Border, and Drop Shadow, for example, although they do not work well with all fonts.

Figure 5: The T at bottom right creates text layers. The dialog lets you enter the text and controls the display.

In a text block, the font settings apply to the entire block, as was the case with Gimp until a few years ago. To work with multiple settings (i.e., a different font for each letter), you need to superimpose multiple layers and align them to create a uniform image. Strangely enough, only Glow provides a way to adjust its parameters; for drop shadows, it would be useful to manage shape and strength.

Functions like Text to Path or similar are not currently supported in Pixelitor. But Use Text for Watermarking will let you create a bump map effect that you can combine with other effects as needed.