Web browsers usually support two types of web images on the browsers; however the third type PNG is also gaining a lot of support. There are many other image formats which are supported by the browsers but the three most well used and supported are

• GIF
• JPG
• PNG
  

GIF Files:

The GIF files commonly known as Graphic Interchange Format were popularized by CompuServe in the 1980s. The GIF files were initiated as a proficient method of spreading images across the data networks. GIF files include a compression system which keeps the file size to a minimum and they also ensure that the images include only web safe colours limited to 256 or fewer colours. There are three types of GIF files.

• Interlaced GIF- These files build a low-resolution version of a full sized GIF picture on the screen while the file is downloading hence giving the viewer a preview of the entire image while the image downloads in the browser.
• Transparent GIF- This format allows picking colours from the colour look up table of the GIF to be transparent. The shortcoming of this file is that it makes every pixel in the graphic that shares the particular colour transparent causing unwanted results. It works best with simple diagrammatic graphics.
• Animated GIF- This format enables you to merge multiple GIF image into a single file to create animation. This format can not apply compression. The animation keeps on playing and cause distraction to the viewer or reader.
  

JPEG Files:

JPEG files known as Joint Photographic Experts Group minimize graphic file sizes and are true colour (24 bit) image format. This format works well for photographic images with gradients, blends and inconsistent colour variations.

JPEG is a lossy format i.e. it throws away bits which means with creation of each image some information is lost which invariably degrades the image quality. So it is advisable to save the original image before working on it.

Progressive JPEG is a newer form of JPEG file which is similar to Interlaced GIF file. The viewer will see a rough picture which will get refined as more and more bits of the image are received. This is good for displaying larger images.

PNG Files:

PNG (pronounced as ping) files or Portable Network Graphics was developed by the graphic software developers association as an alternative to GIF files. This is a new format which is challenging the supremacy of JPEG and GIF image formats.

Unlike JPEG files PNG files do not loose bits while generating the images. PNG files can be made partially transparent which is essential to display good quality of graphics on the web. PNG files support colour depth of more than 24 bits making it a better choice then GIF formatting. This format can also hold short textual descriptions of the image which helps in search engines to index images based on their textual content.

The only shortcoming of PNG files is that they are not as widely supported by web browsers as JPEG and GIF file formats. Moreover, the present executions of PNG graphics in the major web browsers do not completely support all the features of PNG.

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