For normal users, GIMP will seduce you with its advanced functions for web images and formats. You can easily create animations and optimize your art for web publishing, and take advantage of GIMP's extensive photo manipulation features.

Power users, publishers and document management specialists truly benefit from GIMP through its advanced scripting capabilities and the programs' function accessibility.

GIMP, like most Free Software graphic design applications, suffers from the fact that prepress standards, such as PANTONE^® Color Systems, are proprietary and closed. So for GIMP, it means that there are no usable implementations of these standards. Also, because the press world is dominated by Apple-compatible computers you will have to put in some extra effort to print professionally with GIMP, although it is feasible. Another limitation is the internal 8 bit-per-channel representation for images, which may not be sufficient for the professional digital photographer (16 bits-per-channel would be required).

GIMP includes extensive documentation. If the gimp-help package is installed, pressing the F1 key lets you access a help index for the current “active” item, and pressing Shift-F1 gives you access to contextual help.

On the net, GIMP is a very well documented application and a lot of information is freely available. Please refer to The GIMP web site for more information about the available GIMP documentation.

From GIMP's main window (called the tool box), you can access the basic program options such as opening a file, creating a new file, etc.

Once an image is opened or created, you can right-click in the image window and access the image's specific options such as Close, Save, Save as, Dialogs, Filters, etc. We call this the “image menu” in the following sections.

Some of the key concepts to grasp in order to truly benefit from an advanced graphic design application like GIMP are those to do with layers, formats and file modes. Roughly put, digital image editing adds a 4^th dimension: layers. Images are built vertically (as are animations), and each layer has user-defined properties which determine other tasks that can be accomplished. File mode defines the inner logic of the graphic elements. Hence, an RGB image allows for different operations and capabilities that you would not have for a gray scale image. Finally, the file format also impacts on which operations can be done on that file.

If you face difficulties accomplishing any task described below, check those three elements before jumping to conclusions.

Opening a File. Choose File → Open from the menu. Your image appears in a new window. From that window, you can access the image's menu (File, Edit, Select, etc.) or right-click as explained in Section 1.1.3.2, “Right-clicks”. Depending on the file format you want to open, you may have to answer some questions pertaining to the details of that format and its conversion. Keyboard shortcut: Ctrl-O.

Creating a New File. Choose File → New from the menu. A dialog appears allowing you to determine image dimensions in different measurement units (pixels, inches, millimeters, etc.), image orientation (landscape or portrait) and some advanced options (see Figure 5.2, “Creating a New File”). You may also specify a Template from the pulldown list and have most image parameters filled for you. Once you click on the OK button the image is created in a new window. Keyboard shortcut: Ctrl-N.

Figure 5.2. Creating a New File

Saving a File. The first time you Save, or when you Save as, a dialog pops up which allows you to set the name and location of your image. More importantly, this is the place to define the file type such as JPEG or PNG. Keyboard shortcut: Ctrl-S for Save, Shift-Ctrl-S for Save as.

	Note
	New users, at the stage of saving their work, run into multiple problems such as losing layers or simply damaging their work. Most of these problems come from the specific options allowed for each file format. If you have no idea, preserve the image format or save in XCF, GIMP's own file format. You can always try saving the image under different formats later.

The tool box contains your basic graphic design tools. If you move your mouse over any item, its name and keyboard shortcut pops up in a help balloon. Tool options are accessible through the Active Tools Options section of the tool box. We will not detail each tool in this guide as there are already books written about GIMP to assist you. Remember that all operations take place in the current active layer.

	Note
	If you close the tool box, GIMP and all windows are closed. Closing any other window only affects that window.

Figure 5.3. GIMP Picture

This window manages either new or opened images and it is where tools selected in the tool box may be used.

At the bottom of the image window is a numeric value shown as a percentage. This is the zoom ratio. Click on it to choose another zoom ratio. You can also press the + key to increase zoom or the - key to decrease it. Press the 1 key to set zoom to 100%.

	Tip
	Go to menu entry View → Navigation Window to launch a window navigator allowing you to pan and change the zoom ratio of an image window.

All operations can be undone and redone. You can change how far, as a minimum, you can go back in the commands “history” and how much memory to reserve for it, by choosing File+Preferences from the menu, then selecting the Environment section. Please bear in mind that both settings have a large impact on RAM usage which might make it difficult, or even impossible, to manipulate a large image file.

Choose Edit → Undo from the image menu, or press the Ctrl-Z keys, to undo the last operation.

Choose Edit → Redo from the image menu, or press the Ctrl-Y keys, to redo the last undo operation.

GIMP allows you to copy (Ctrl-C), cut (Ctrl-X) and paste (Ctrl-V) within any window, as well as between any GIMP image window. You can also paste as layers.

Choose Dialogs → Layers (or press the Ctrl-L keys); Dialogs → Channels; Dialogs → Paths from the image menu to access the layers, channels and paths dialogs respectively (see Figure 5.4, “Layers, Channels and Paths Dialogs”).

Figure 5.4. Layers, Channels and Paths Dialogs

GIMP allows for an unlimited number of layers. Each layer has a specific set of properties.

In a RGB color image there are three channels, one for red, one for green and one for blue. The channels dialog lets you turn a channel off or on, as well as add and remove other channels. Clicking on the eye at the left of a channel name turns it on or off depending of its original status.

Paths let you manipulate your selections in very complex ways. You can transform selections into paths which let you treat the selection as a curve, giving you more control over it since you can, for example, add points to the curve to manipulate it.

Filters are a set of programmed actions which modify your image according to specified options. GIMP offers a vast range of filters such as blurs, noise effects or image enhancement operations that may be applied to selections and layers. Feel free to explore them all.

Figure 5.5. Filter's Menu

Figure 5.6. Color Selection Dialog

Choose the Dialogs → Colors menu to open the color selection dialog. Use the buttons at the top to select the color “space” you want to use for color selection: GIMP (which lets you select colors using different palettes: Red, Green, Blue, Hue, Saturation and Value), CMYK, color triangle, watercolor, a reduced color palette or scales. The fore/background colors are handled the same way they are in GIMP's tool box. Selected colors are active immediately after choosing them. Rule of thumb: try to work in RGB so you can have a wider number of formats to save your work into.

Figure 5.7. Brushes Dialog

This dialog lets you define the type and size of the brushes which apply to most drawing and erasing tools. Click on the active brush section of the tool box, or choose the Dialogs → Brushes menu to open this dialog. Keyboard shortcut: Ctrl-Shift-B.