Graphics File Formats

Graphics files contain information that describes images. An application must be able to interpret graphic formats in order to read or display a graphics file. A text editor or a word processing program can't correctly open a graphics file to produce a picture, although you can insert a graphics file into OpenOffice documents.

The information stored in a graphics file can be in one of several formats, with different purposes. Usually the file has an extension that identifies the type of format. Graphics applications save files with the appropriate extension. However, because Linux recognizes file types by information inside the file, rather than by the extension, when using a Linux application, you might see a message stating that the file extension does not match the file format. Some common formats are shown in Table 13-1.

Table 13-1. Graphics File Formats

Ext	Name	Used for	Advantages/Disadvantages
.bmp	MS Windows bitmap format	MS Windows graphics files	Recognized by most Windows applications.
.gif	Graphics Interchange Format	Web page images: line drawings, cartoons	Better quality than .jpg for images with 256 or fewer colors. Used for animated graphics.
.jpg	Joint Photographic Experts Group	Most used type for Web page images: photographs, art	Better quality for photographs than .gif. Smaller file size than .png.
.png	Portable Network Graphics	General graphic images; recognized by browsers	Newer format designed to replace .gif. A universal format with no patent restrictions. Smaller file size than .gif. Better transparency support. No animation support.
.tif	Tagged- Image File Format	Popular for graphics exchanged between operating systems	Early type that was designed to be hardware and OS independent. The newer .png format is better suited to exchange in many environments.

You can convert files from one format to another. You can read a file into an application and use Save as to save the file in a different format. If you want to convert quickly, without editing, use the convert command at the command line. For example, to convert an existing .gif file to a .jpg file, use:

 convert rose.gif rose.jpg