File Formats
The GIMP has support for a wide range of still image and video file formats.
Supported Formats
The following table lists the formats supported by GIMP:
Table 2-1. File Formats
| Read | Write | |
|---|---|---|
| AA - ASCII Art | N | Y |
| AVI - Audio/Video Interleave | Y | Y |
| BMP - Bitmap | Y | Y |
| C - "C" Source | N | Y |
| CEL - CIMFast Event Language | Y | Y |
| FITS - Flexible Image Transport System | Y | Y |
| FLI - Autodesk FLIC Animation | Y | Y |
| GIF - Graphics Interchange Format [a] | Y | Y |
| H - "C" Header File | N | Y |
| HRZ - Slow Scan Television | Y | Y |
| HTML - Formatted Table | N | Y |
| JPEG - Joint Photographics Expert Group | Y | Y |
| MIFF - Magick Image File Format | Y | Y |
| MPEG - Motion Picture Expert Group | Y | N |
| PCX - PC Paintbrush | Y | Y |
| PIX - Inset Systems Bitmap | Y | Y |
| PNG - Portable Network Graphics | Y | Y |
| PNM - Portable Anymap | Y | Y |
| PSD - Photoshop Document | Y | N |
| PSP - Paint Shop Pro | Y | N |
| PS - PostScript | Y | Y |
| SGI - Silicon Graphics | Y | Y |
| Sunras - Sun Raster | Y | Y |
| TGA - Targa Bitmap | Y | Y |
| TIFF - Tagged Image File Format | Y | Y |
| WMF - Windows Meta File | Y | N |
| XBM - X Bitmap | Y | Y |
| XCF - GIMP Native | Y | Y |
| XWD - X Window Dump | Y | Y |
| XPM - X Pixmap | Y | Y |
| Notes: a. You need a license from Unisys to legally save files in this format. | ||
What Format Should Be Used?
When saving an image, an appropriate decision should be made with regards to the file format chosen to do so. Some of the more popular formats are mentioned below.
- XCF: The native file format of The GIMP
When saving images that are not yet complete and there is intent to continue working later, the most appropriate file format to choose is XCF. This file format is the native file format that The GIMP uses. XCF supports many features including compression.
While XCF is an excellent choice in file format, it is not as portable as one might like. It is wise to save images that are not for use exclusively from within The GIMP using a differing format.
See also: XCF Glossary entry
- PNG: Portable Network Graphics
PNG can preserve all the transparency and color of an image and uses powerful lossless compression to reduce file sizes. In particular, computer-generated images usually compress very well.
PNG supports smooth 8-bit transparency which can make for exceptional zero loss web graphics, but a caveat. Some browsers do not fully support all of the features that PNG offers. As always, check compatibility between the viewer and the format before commiting to a particular format.
- JPEG: Joint Picture Expert Group
Photographs and other images from the real world (which include most images taken with digital cameras and color scans) can be compressed very effectively with JPEG.
JPEG images are compressed using a semi intelligent lossy algorithm that is very good at fooling the human eye. This format is excellent for saving on space and preserving viewable quality, but there are many situations where JPEG is an unsuitable format to choose. If the image contains broad bands of single color or is mechanical in nature (many broad straight single color areas), JPEG is a bad choice of format. Another note to make is that repeated saving of images that are JPEG encoded will result in degredation to quality over each save. As with any powerful option, be aware of this format's lossy compression method, and ensure the choice of JPEG is not made lightly.
The JPEG filter used by The GIMP utilizes JFIF compression for compatibility with most existing software. It allows you to adjust the quality of the image and see immediately how the saved image will look and how big the file will be.
- GIF: Graphics Interchange Format
Unlike all the other file formats described here GIF requires the use of a colormap. This means that a maximum of 256 different colors will be preserved in the saved image. The GIMP can perform the conversion automatically, but the results may sometimes be disappointing due to this limitation of GIF.
Despite the poor compression and limited number of colors, there are two desirable features of GIF for web designers. GIF is non lossy, so no image data is lost over saves, and GIF supports animation and transparency. The GIMP supports both of these features fully.
Support for creating GIFs may not be included in your version of The GIMP due to patent problems.
- BMP: Windows Bitmap
This format is often used by applications for Microsoft Windows. Full color images can be stored in this format, but shortcomings of the compression scheme mean that the resulting files may be quite large. Image resolution is preserved, but no other metadata is stored in the BMP format.
Some web browsers have included support for viewing BMP images but this is not common, so you should avoid using them on the web.
- XPM: X Pixmap
This format is sometimes used by applications for the X Window System. The files created can be compiled directly into a program by a software developer, but this convenience comes at a price of much increased file size. You will probably already know if this feature is useful to you.
Some web browsers have included support for viewing XPM images but this is not common, so you should avoid using them on the web.
- TIFF: Tagged Image File Format
One of the oldest formats still commonly in use today, TIFF is a very powerful but complicated format. If the need to export images from The GIMP to a package which doesn't support any of the other formats mentioned earlier in this section, it will probably accept TIFF.
TIFF can preserve all the transparency and color of your original image, but you may lose some of this information when importing the TIFF into another package.