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Graphics and multimedia file formats

It has been said that "The wonderful thing about standards is that there are so many to choose from" and that is true of graphics and multimedia file formats.


A Windows BitMaP format that is widely used in the PC world. It is also supported by some Macintosh programs (Adobe Photoshop) and can be opened by QuickTime's translators (use MoviePlayer or the PictureViewer application.)
BMP files support a range of color depths (B&W, 16 colors, 256 colors, 16 bit and 24 or 32 bit true color.) These graphics are usually not compressed; there is a compression option, but it is not supported by all applications.

CompuServe's Graphics Interchange Format (GIF) is a compressed format developed for exchanging graphics via a modem. It is limited in that it does not support bit depths greater than 8 bits.
Unlike compression formats such as JPEG, GIF compression is non-lossy; the saved file is no different to the original (unless you had to reduce the bit-depth of the illustration.)
GIF has become very popular because it is one of two graphics formats supported by nearly all web browsers (the other being JPEG.) It also supports transparency and interlaced display. With transparency a color can be defined as the transparent color, and when the graphic is displayed in the browser the background graphic in the HTML page can be seen through those pixels. Interlaced graphics are saved i the file as a sequence of alternate lines. As the file is read, the lines are read in and duplicated, then the other lines filled in as the rest of the file is downloaded. For example, the program might get lines 1, 5, 15, etc (so it would duplicate line 1 for lines 1 through 5) and then it would get lines 3, 7 and so forth. The advantage of this technique is that the browser can display a graphic much faster than it would be able to if it waited until the entire file was downloaded.
GIF also supports sequences of images which play as an animation. You can define the time that each frame is displayed, as well as how many times the sequence plays.
GIF uses LZW compression, which is a patented algorithm owned by Unisys. This is of most concern to graphics application developers who want to support the format.
Programs that support GIF include:

  • Adobe PhotoShop
    Still frames. Lets you specify transparent and interlaced graphics
  • Adobe ImageReady
    Still images, as well as sequences of images.
  • GifBuilder
    Macintosh only application.


The PICS format was an attempt by several Apple graphics applications developers to manage the problems inherent in shifting animation sequences around as individual image files. Apple didn't develop the PICS format, but PICS briefly became a defacto standard for the Macintosh because it provided an easy method of linking several PICT files into a single file.
The PICS format includes an optional method for reducing the size of the files. This option anables the program that creates the PICS file to save only the changes that occur from one frame to the next. This compression can greatly reduce the size of the file.
QuickTime has made the PICS format redundant.


Graphics format developed by Apple for storing both bit-map and vector graphics (though it is primarily used for bit-map graphics these days.) It is the most common graphics format on the Macintosh, and is supported by most applications that support graphics.
Windows users can open PICT files using either Adobe Photoshop, or the PictureViewer application included with QuickTime 3.0


The Tagged Image File Format (TIFF) was developed for scanned images back when there was no great format for storing large, bit-mapped graphics. TIFF remains in use, though other file formats have evolved where they can be used to store these graphics (PICT, BMP can do it, Photoshop uses it's own file format.)
The greatest disadvantage is that TIFF offers only one compression option which is not as efficient (both in file size and the amount of time it takes to compress) as other file formats now support. If you are working in publishing you might want to stick with TIFF, but for multimedia, you'll probably find it better to use PICT, BMP or JPEG.


last updated: 6/11/98

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