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Summary for image file formats

Uses for GIF, PNG and JPEG files

Now that Netscape and other browsers are supporting both GIF and JPEG graphics in inlined Web page images you could use either graphic format for the visual elements of your Web pages. However, in practice most Web developers will continue to favour the GIF format for most page design elements, and choose the JPEG format mostly for photographs, complex "photographic" illustrations, medical images, and other types of images where the compression artifacts of the JPEG process do not severely degrade image quality.

Advantages of GIF Files

Examples of various GIF images.
  • The most widely supported graphics format on the Web
  • Has an animation ability for cartoon like activity
  • All graphic Web viewers support the GIF format for inlined images.
  • GIF supports transparency and interlacing.
  • GIFs of diagrammatic images look better than JPEGs.

Advantages of JPEG Images

Jpeg examples
  • Huge compression ratios are possible, for faster download speeds.
  • Supports full-colour images (24-bit "true colour" images).
  • MPEG is the equivalent to animation it is used by digital cameras making short films
  • Gives excellent results in most photographs and medical images.

What about TIFF?

The TIFF image format has been around for a long time, and will likely be around for quite a while more. The TIFF format was the cross-platform image format by choice until PNG was introduced, and according to some still is. TIFF's are a developer's nightmare. Last I counted there was over 50 different styles of TIFF images. You never know if an application will be able to read a TIFF image or not. One of the more popular TIFF's is the 24-bit LZW compressed version. This has the same patent restrictions as the GIF format does, but until PNG, was the only standard lossless compressed format. The standard 24 Bit PNG functionally is very similar in function to a LZW compressed TIFF. The TIFF format is able to store multiple images in one file. This is commonly used for FAX images. PNG's do not have this capability. The TIFF format remains to be popular, but there are few reasons to use it with the added benefits of PNG.

PNG advantages

Rotating image
  • multiple CRCs so that file integrity can be checked without viewing
  • check digit that can detect the most common types of file corruption
  • better compression than GIF, typically 5% to 25% (but often 40% or 50% better on tiny images)
  • non-patented
  • completely lossless compression
  • major gnarly two-dimensional interlacing scheme 1-, 2-, 4- and 8-bit palette support (like GIF) 1-, 2-, 4-, 8- and 16-bit greyscale support 8- and 16-bit-per-sample (that is, 24- and 48-bit)
  • truecolour support full alpha transparency in 8- and 16-bit modes,
  • not just simple on-off transparency like GIF ``palette-alpha'' mode, effectively transforming normal RGB palette into RGBA gamma correction for cross-platform ``brightness'' control
  • colour correction for cross-platform, precision colour both compressed and uncompressed
  • text chunks for copyright and other info
  • free and complete reference implementation with full source code
  • officially registered Internet media (MIME) type: image/png

And finally

There are some important issues here about standards. GIF and JPEGs are de facto standards. whereas because PNG has the backing of the W3C it is a true standard. The problems with TIFF show all of the issues of what happens when standards change too rapidly. These units relate strongly to module 2 of the AS level course and would make good examples in it.

 
   

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