Gimp

We often think in stereotypes, and the software market is no exception. Besides Windows, there are many interesting operating systems, documents do not have to be typed in MS Word, and photos can be processed not only in Adobe Photoshop.

To process bitmap graphics on a professional level is the destiny of expensive, powerful software. However, nowadays not only professionals and amateur photographers are involved in digital image processing, but also a wide range of users who are far from this “labor” segment.

What does the average user need? Everyone wants a simple, easy-to-learn program that works stably and lets you perform all the necessary operations.

GIMP stands for GNU Image Manipulation Program. The free-licensed graphic editor has a funny logo with a little devil in it, which isn’t a coincidence because its name contains the anagram “imp”. GIMP works in all popular operating systems: Linux, Windows and Mac OS X. GIMP is included in almost all popular Linux distributions, so it does not require a separate installation. If the program does not appear in the start menu of a desktop environment (KDE, GNOME, etc.), it simply needs to be installed from the distribution disks using the standard means (for example, in SuSE YaST2 is responsible for software installation). Installing the editor in Windows requires the GTK+ library. You can download the library (3.7MB) and the editor (7.8MB) from the GIMP for Windows page. The library and editor have international modules and do not require additional russification to be downloaded. GIMP has rather modest system requirements in comparison with other graphics editors, successfully running even on old computers with 128MB RAM. The minimum requirements for the processor make the older generation hit a distant memory: Pentium MMX. But even allowing for the fact that the real system requirements of the software are always much higher than the officially stated minimum, GIMP will feel confident on all workstations built in the current millennium.

Interface

The first start-up of GIMP is fairly quick, but the opening of its main window may be confusing to new users.

The editor’s interface seems unusual, to say the least. Instead of the usual program window with an extensive main menu and toolbar, we have a tiny concentration of buttons. But as soon as you open an image, the situation becomes more or less clear – the documents open in independent windows with the main menu already present. The start window acts as a kind of quick access panel, where all the most frequently used functions are collected. The other tools can be called in several ways. The first, the most guessed method, is to navigate through the main menu of the document working window. The second is by using the right mouse button. Instead of the usual invocation of the properties of the current object, you will be offered a complete list of editor functions, duplicated by the main menu. If you click the left mouse button near the top edge of the opened menu, it will turn into an independent window, which can also be used as a toolbar for a shortcut.

And finally, the third way is the hotkeys. Call the program settings from the main window and go to the “Interface” tab. Turn on the “Use shortcuts” and “Save shortcuts on exit” options. This allows you to assign shortcuts directly while the editor is running. The most frequently used functions can be invoked with hotkeys initially. But if your priorities are different from what the developers intended, why not add your own shortcuts to the list? You can also reassign existing hotkeys. In order to assign/reassign a shortcut, you need to get to the desired menu item, but do not select it. Stop the mouse cursor on it and press any key combination. A pointer appears to the right of the item name stating that the shortcut is now assigned to the current tool.

The open dialogs and save files are in the standard GTK+ tradition, which is familiar to Linux users, but may seem inconvenient to Windows users.

Image processing: from RAW to the final result

A graphics editor is most often a tool for image processing, to improve the quality of images. Let’s take a look at GIMP as a tool for a wide range of image processing tasks. The most common way to start is to convert a RAW image to JPEG or TIFF. During the conversion process you can adjust the images by adjusting the exposure, white balance, and other parameters. The GIMP distribution does not have a built in RAW conversion tool, so a special extension must be loaded. For example, UFRaw. If you are working in Windows, you can immediately download the ufraw-0.7-setup.exe package to install. For Linux users, there is a set of packages compiled for different distributions. If your distribution is not on the list, download the source code of the extension and compile it yourself with the standard commands:
./configure
make
make install
The default build does not include support for EXIF display, but you can manually enable it by specifying the additional switch –with-libexif

After the extension is installed, a raw image appears in the list of available file types when we open the files. Now we can open the RAW of almost any modern camera.

The extension supports the display of two histograms: RAW (internal) and Live (real). With the Exposure control you can change the overall level of image illumination (automatic mode is present). Adjustment of the image is made with the help of tools located in four tabs.

• WB. Adjusts the white balance. There is an auto mode.
• Base. Adjustment of exposure with the help of curves.
• Color. Adjusts brightness and contrast, and sets color profiles.
• Color. Adjust color saturation.

When all manipulations are complete, you can open the image in the editor. If you take pictures in JPEG, you will need to perform all of the above operations in the editor itself.

The exposure and color balance adjustments are made with the help of “Curves”.

By controlling the three channels simultaneously (Brightness), we adjust the exposure, and by transferring the control to the individual channels, we can control the white balance. In addition, the color balance can be adjusted with the tool of the same name.

You can separately adjust the balance in three segments of the dynamic range: shadows, midtones and highlights.

Noise is reduced with the “Selective Gaussian Blur” filter. In the filter settings you should specify the blurring radius, as well as the maximum difference between neighboring pixels that the filter will pay attention to.

You sharpen your images using the “Blur Mask” filter. You specify the radius of sharpening, the degree to which the filter is applied, and the minimum threshold for applying it.

The red-eye removal procedure in GIMP is a very time-consuming process. Using the “Elliptical Area Selection”, select the red eye. Then open the Channels dialog box and leave only the red channel visible. Go to “Curves” and lower the channel intensity graph. Turn on the other channels again and observe the result.

You can also download a special extension for redeye removal – redeye. Windows users only need to download the ZIP-archive which is a packed exe-file. Linux users should download the source code of the extension and install it with the command:
gimptool-2.0 –install redeye.c

After installing the extension, a new Misc group appears in the filters, with Red Eye Remover and Auto Red Eye Remover items. Next, you simply select the rectangular area around the pupil and apply the filter.

When processing images, it is quite often necessary to resort to layers. Let’s consider the operation of layers on the example of soft focus effect emulation. The Layer List window is called with the Ctrl+L key combination. Create a new layer as a copy of the current one. On the new layer, apply the “Gaussian Blur” filter with a radius of 15 pixels. After that, set the transparency of the layer to around 30-50%. The image looks as if a special filter or lens was used to take the picture.

Photographers are not snipers. Very often the model being shot is not in the center of the frame, and there is unnecessary detail in the composition. In addition, non-SLR cameras have sensors with a 4:3 aspect ratio, while printing requires a 3:2 aspect ratio. In such cases it is customary to crop the image, that is, to cut off the edges. GIMP allows you to crop an image with the mouse, moving and scaling the edges of a frame. You can also set the coordinates of the frame boundaries manually in the toolbox, and, importantly, specify the aspect ratio of the image.

When all the transformations are done, you can safely save the file to your hard drive.Free: “cheese” or real benefit?

Of course this article was only a small part of what GIMP can do. GIMP can be used for painting, taking screenshots, making nice logos, stylizing photos, and much more. What is important is not the absolute number of features, but the quality of the editor and its usability. Of course, GIMP is inferior to Adobe Photoshop in terms of professional use. But if we look at the purely amateur level, for free we get a high quality, stable product with a lot of possibilities.

Instead of an afterword

The latest stable version of GIMP at the time of writing is 2.2.10. At the same time, a new version of the editor is being developed. Not so long ago NewsForge published an article about what to expect in the new 2.4 version of the editor.