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 I Use?
When saving a file, you need to decide which file format to use. There are descriptions of some important and popular formats below to help you choose the right one for your images.
- XCF: GIMP's Native Format
If you're saving an image that's not "finished" and intend to continue working on the image in GIMP later, you should always save it as XCF. XCF preserves all of your image's layers, channels, and masks, as well as your paths, guides, selections, and other important details.
However, XCF is only suitable for GIMP. If you want to share your image or put the image on the web, you should probably use another file format as well as XCF because most web browsers, image viewers, and other software packages cannot read XCF.
- PNG: Portable Network Graphics
PNG can preserve all the transparency and color of your original image and uses powerful lossless compression to reduce file sizes. In particular, computer-generated images usually compress very well.
Although PNG supports smooth transparency, today's most popular web browsers still don't. While we wait for Microsoft to catch up, you'll probably want to stick with non-transparent PNGs on web pages. You can use transparency effectively elsewhere though.
- JPEG: Compressed Photographic images
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. Usually screenshots, logos, and computer generated images will not benefit from JPEG.
The JPEG method is lossy, which means that, although the saved image will appear almost identical to the original, it will actually have hidden detail removed. You should not use it on images that you intend to do additional processing on later because the loss is exaggerated by repeated use.
GIMP's JPEG filter uses JFIF files for compatability 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: Compuserve GIF
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. GIMP can handle 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. They are simple forms of transparency and animation. GIMP's GIF filter supports both of these features.
Support for creating GIFs may not be included in your version of 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 you need to export images from 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.