Kapitola 6. Getting Images out of GIMP


1. Files
1.1. Save / Export Images
1.2. File Formats
2. Příprava obrázků pro web
2.1. Images with an Optimal Size/Quality Ratio
2.2. Vyšší komprese obrázků
2.3. Saving Images with Transparency

1. Files

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

1.1. Save / Export Images

[Poznámka] Poznámka

When you open an image, let's say in JPG or PNG file format, it is imported into GIMP's own XCF format, as a new project.

For example, a sunflower.png image will be loaded as *[sunflower] (imported)-1.0 (indexed color, 1 layer). The leading asterisk indicates that this file has been changed. This image can be saved as sunflower.xcf by using the Save command. If you need your image in another format, you should use the Export command.

When you are finished working with an image, you will save the results. In fact, it is often a good idea to save at intermediate stages too. GIMP is a pretty robust program, but on rare occasions crashes have happened.

GIMP's native format XCF is special. It is the only format that can store everything about an image (with the exception of undo information). This is the reason that saving can only be done in this format. It makes the XCF format especially suited for storing intermediate results, and for saving images to be re-opened later in GIMP.

XCF files are not readable by most other programs that display images. Once you have finished editing your image, you can export it to the format of your choice. GIMP supports a wide range of formats. Most file formats that can be imported, can also be used for exporting.

1.2. File Formats

There are several commands for saving and exporting images. They are listed in the section covering the File Menu. More information on how to use them can be found there.

GIMP allows you to export 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. It is up to you to understand the capabilities of the format you choose.

Exporting an image does not modify the image itself, so you do not lose anything by exporting. See Export file.

[Poznámka] Poznámka

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 (an asterisk is in front of the image name).

Obrázek 6.1. Closing warning

Closing warning

Saving an image in GIMP's native format XCF will cause the image to be considered "not dirty". On the contrary, exporting an image will not change it to "not dirty", because GIMP can't know for sure that no image information will be lost.