ART (file format)
ART is a proprietary image file format used mostly by the America Online (AOL) client software. The ART format (file extension ".art") holds a single still image that has been highly compressed. Originally, the compression was developed by the Johnson-Grace Company, which was then acquired by the AOL service. When an image is converted to the ART format, the image is analyzed and the software decides what compression technique would be best. Internet Explorer used to be able to display ART images but now is no longer capable.
The AOL service can automatically convert images downloaded from the Internet to the compressed ART format. This conversion, which can be turned off, reduces download time for the image file. Image display problems with the AOL web browser are addressed at America Online webmaster FAQ entry. An art file opened with AOL picture viewer can be saved as another file type.
ART files can be batch converted to BMP, JPG, and other file formats with rare graphics programs, such as Graphic Workshop Professional  with an .art plug-in. Old versions of Internet Explorer can open and convert ART files to BMP files, through the File/Save As command. 
- Johnson-Grace Company official Web site via the Internet Archive
- "Profile - Irving Reed": An article with information on the history of Johnson-Grace and the ART image compression.
- "Optimizing Web Graphics: Compression": A webreference.com article with technical details on the ART image format.
- Graphics Questions: An America Online webmaster FAQ entry on graphics display problems.
- Template:US patent Data compression using adaptive bit allocation and hybrid lossless entropy coding
- Template:US patent Optimal spline interpolation for image compression
- Template:US patent Method and apparatus for compressing imagesde:ART (Dateiformat)