GIMP (the GNU Image Manipulation Program) is a program for creating and editing raster graphics. In most aspects, its features are comparable to those of

Adobe* Photoshop* and other commercial programs. Use it to resize and retouch photographs, design graphics for Web pages, create covers for your custom CDs, or almost any other graphics project. It meets the needs of both amateurs and professionals.

GIMP is an extremely complex program. Only a small range of features, tools, and menu items are discussed in this chapter. See Section 18.8, “For More Information” for ideas of where to nd more information about the program.

18.1 Graphics Formats

There are two main types of digital graphics: raster and vector. GIMP is intended for working with raster graphics, which are most often used for digital photographs or scanned images.

Raster Images. A raster image is a collection of pixels: Small blocks of color that create an entire image when put together. High resolution images contain a large number of pixels. Because of this, such image les can easily become quite large. It is not possible to increase the size of a raster image without losing quality.

GIMP supports most common formats of raster graphics, like JPEG, PNG, GIF, BMP, TIFF, PSD, and more.

Vector Images. Unlike raster images, vector images do not store information about individual pixels. Instead, they use geometric primitives such as points, lines, curves, and polygons. Vector images can be scaled very easily. Depending on their content, vector image les can both be very small or very large. However, their le size is usually independent of their display size.

The disadvantage of vector images is that they are not good at representing complex images with many colors such as photographs. There are many specialized applications for vector graphics, for example Inkscape. GIMP has very limited support for vector graphics. For example, GIMP can open and rasterize vector graphics in SVG format or work with vector paths.

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GIMP supports only the most common color spaces:

RGB images with 8 bits per channel. This equals 24 bits per pixel in RGB images without an alpha channel (transparency). With an alpha channel, that equals 32 bits per pixel.

Grayscale images with 8 bits per pixel.

Indexed images with up to 255 colors.

Many high-end digital cameras produce image les with color depths above 8 bits per channel.

If you import such an image into GIMP, you will lose some color information. GIMP also does not support a CMYK color mode for professional printing.

18.2 Starting GIMP

To start GIMP, select Applications Graphics GIMP.

18.3 User Interface Overview

By default, GIMP shows three windows. The toolbox, an empty image window with the menu bar, and a window containing several docked dialogs. The windows can be arranged on the screen as you need them. If they are no longer needed, they can also be closed. Closing the image window when it is empty quits the application.

In the default conguration, GIMP saves your window layout when you quit. Dialogs left open reappear when you next start the program.

If you want to combine all windows of GIMP, activate Windows Single-Window Mode.

18.3.1 The Image Window

If there is currently no image open, the image window is empty, containing only the menu bar and the drop area, which can be used to open any le by dragging and dropping it there. Every new, opened, or scanned image appears in its own window. If there is more than one open image, each image has its own image window. There is always at least one image window open.

In Single-Window Mode, all image windows are accessible from a tab bar at the top of the window.

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The menu bar at the top of the window provides access to all image functions. You can also access the menu by right-clicking the image or clicking the small arrow button in the top left corner of the rulers.

The File menu oers the standard le operations, such as New, Open, Save, Print and Close. Quit quits the application.

With the items in the View menu, control the display of the image and the image window.

New View opens a second display window of the current image. Changes made in one view are reected in all other views of that image. Alternate views are useful for magnifying a part of an image for manipulation while seeing the complete image in another view. Adjust the magnication level of the current window with Zoom. When Fit Image in Window is selected, the image window is resized to t the current image display exactly.

18.3.2 The Toolbox

The toolbox contains drawing tools, a color selector, and a freely congurable space for options pages. If you accidentally close the toolbox, you can reopen it by clicking Tools New Toolbox.

To nd out what a particular tool does, hover over its icon. At the very top, there is a drop area which can be used to open any image le by simply dragging and dropping it there.

FIGURE 18.1: THE TOOLBOX

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The current foreground and background color are shown in two overlapping boxes. The default colors are black for the foreground and white for the background. Swap the foreground and background color with the bent arrow icon to the upper right of the boxes. Use the black and white icon to the lower left to reset the colors to the default. Click the box to open a color selection dialog.

Under the toolbox, a dialog shows options for the currently selected tool. If it is not visible, open it by double-clicking the icon of the tool in the toolbox.

18.3.3 Layers, Channels, Paths, Undo

Layers shows the dierent layers in the current image and can be used to manipulate the layers.

Information is available in Section 18.6.6, “Layers”.

Channels shows the color channels of the current image and can manipulate them.

Paths are a vector-based method of selecting parts of an image. They can also be used for drawing. Paths shows the paths available for an image and provides access to path functions.

Undo shows a limited history of modications made to the current image. Its use is described in Section 18.6.5, “Undoing Mistakes”.

18.4 Getting Started

Although GIMP can be a bit overwhelming for new users, most quickly nd it easy to use after they work out a few basics. Crucial basic functions are creating, opening, and saving images.

18.4.1 Creating a New Image

1. To create a new image, select File New. This opens a dialog in which you can make settings for the new image.

2. If desired, select a predened setting called a Template.