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Chapter 5.  Using GIMP as a Beginner

1.  Files

The GIMP is capable of reading and writing a large variety of graphics file formats. With the exception of GIMP's native XCF file type, file handling is done by plug-ins. Thus, it is relatively easy to extend GIMP to new file types when the need arises.

Not all file types are equally good for all purposes. This part of the documentation should help you understand the advantages and disadvantages of each type.

1.1.  Creating new Files

You can create new files in GIMP by using the following menuitem: File->New. This opens the Create a new image dialog, where you can modify the initial width and height of the file or using the standard values. More information about this dialog can be found in Section 5.2, “ New.

1.2.  Opening Files

There are several ways of opening an existing image in GIMP:

Open File

The most obvious is to open it using a menu, by choosing File->Open from either the Toolbox menu or an image menu. This brings up a File Chooser dialog, allowing you to navigate to the file and click on its name. This method works well if you know the name of the file you want to open, and where it is located. It is not so convenient if you want to find the file on the basis of a thumbnail.

Figure 5.1.  The “File Open” dialog.

The File Open dialog.

GIMP 2.2 introduced a new File Chooser that provides several features to help you navigate quickly to the file you are looking for. Perhaps the most important is the ability to create “bookmarks” for folders that you use often. Your list of bookmarks appears on the left side of the dialog. The ones at the top ( “Home”, “Desktop”, etc) come automatically; the others you create using the “Add” button at the bottom of the list. Double-clicking on a bookmark takes you straight to that directory.

At the center of the dialog appears a listing of the contents of the selected directory. Subdirectories are shown at the top of the list, files below them. By default all files in the directory are listed, but you can restrict the listing to image files of a specific type using the File Type selection menu that appears beneath the directory listing.

When you click on a file entry in the listing, if it is an image file, a preview will appear on the right side of the dialog, along with some basic information about the properties of the image. Note that previews are cached when they are generated, and there are some things you can do that may cause a preview to be incorrect. If you suspect that this may be happening, you can force a new preview to be generated by holding down the Ctrl key and clicking in the Preview area.

One thing that strikes many people when they first see the File Open dialog is that there is no way to enter the name of the file using the keyboard. Actually this can be done, but the feature is a bit hidden: if you type Ctrl-L with the dialog focused, an "Open Location" dialog pops up, with a space to type the file name. This dialog is described in more detail below.

[Note] Note

In the great majority of cases, if you select a file name from the list, and click the “Open” button in the lower right corner or the dialog, GIMP will automatically determine the file type for you. On rare occasions, mainly if the file type is unusual and the name lacks a meaningful extension, this may fail. If this happens, you can tell GIMP specifically what type of file it is by expanding the “Select File Typ” option at the bottom of the dialog, and choosing an entry from the list that appears. More commonly, though, if GIMP fails to open an image file, it is either corrupt or not in a supported format.

Open Location

If instead of a file name, you have a URI (i.e., a web address) for the image, you can open it using the menu, by choosing File->Open Location from either the Toolbox menu or an image menu. This brings up a small dialog that allows you to enter (or paste) the URI.

Figure 5.2.  The “Open Location” dialog.

The Open Location dialog.

The “Open Location” dialog.

Open Recent

If the image is one that you previously created using GIMP, perhaps the easiest way to open it is from the menu, using File->Open Recent. This gives you a scrollable list of the images you have most recently worked on in, with icons beside them. You need only select the one you want, and it will be opened.

File Browser

If you have associated the file type of the image with GIMP, either when you installed GIMP or later, then you can navigate to the file using a file manager (such as Nautilus in Linux, or Windows Explorer in Windows), and once you have found it, double-click on the icon. If things are set up properly, this will cause the image to open in GIMP.

Drag and Drop

Alternatively, once you have found the file, you can click on its icon and drag it into the GIMP Toolbox. (If instead you drag it into an existing GIMP image, it will be added to that image as a new layer or set of layers.)

For many applications, you can click on a displayed image (a full image, not just a thumbnail) and drag it into the GIMP toolbox.

Copy and Paste

For some applications, if the application gives you a way of copying the image to the clipboard, you can then open the image in GIMP by choosing File->Acquire->Paste as New from the Toolbox menu. Support for this is somewhat variable, however, so your best bet is to try it and see whether it works.

Image Browser

In Linux, you might want to take a look at a program called gthumb, an image-management application that in several ways nicely complements GIMP. In gthumb, you can cause an image to open in GIMP either by right-clicking on the icon and selecting GIMP from among the list of options, or by dragging the icon into the GIMP Toolbox. See the gthumb home page for more information. Other similar applications : gqview, xnview

When you open a file, using the File menu or any other method, GIMP needs to determine what type of file it is. Unless there is no alternative, GIMP does not simply rely on the extension (such as ".jpg") to determine the file type, because extensions are not reliable: they vary from system to system; any file can be renamed to have any extension; and there are many reasons why a file name might lack an extension. Instead, GIMP first tries to recognize a file by examining its contents: most of the commonly used graphics file formats have "magic headers" that permit them to be recognized. Only if the magic yields no result does GIMP resort to using the extension.

1.3.  Saving Files

There are several commands for saving images. A list, and information on how to use them, can be found in the section covering the File menu.

GIMP allows you to save the images you create in a wide variety of formats. It is important to realize that the only format capable of saving all of the information in an image, including layers, transparency, etc., is GIMP's native XCF format. Every other format preserves some image properties and loses others. When you save an image, GIMP tries to let you know about this, but basically it is up to you to understand the capabilities of the format you choose.

Figure 5.3.  Example of an Export dialog

Example of an Export dialog

As stated above, there is no file format, with the exception of GIMP's native XCF format, that is capable of storing all the data in a GIMP image. When you ask to save an image in a format that will not completely represent it, GIMP notifies you of this, tells you what kind of information will be lost, and asks you whether you would like to "export" the image in a form that the file type can handle. Exporting an image does not modify the image itself, so you do not lose anything by doing this.

[Note] Note

When you close an image (possibly by quitting GIMP), you are warned if the image is "dirty"; that is, if it has been changed without subsequently being saved. Saving an image in any file format will cause the image to be considered "not dirty", even if the file format does not represent all of the information from the image.

  Published under the terms of the GNU General Public License Design by Interspire