Graphic Format for the Web

For Web pages, use of JPEG and PNG graphics are recommended as it provides maximum
compatibility with all the devices that might be accessing the Web page. For photos, use
of JPEG graphic format and for screen-shots and drawings use of PNG graphic format is
recommended. Both these formats compress the picture information to reduce the
download tie and increase the downloading speed

• JPEG - It uses a lossy compression which means that the image quality is lost in the process of compressing the image. It is recommended that for continuous tone pictures such as photos JPEG should be used. Most JPEG editor allows the user to specify the amount of detail that the user is prepared to lose. If the quality is reduced, then the loss is visible; JPEG is about half the size of PNG.

• PNG - It uses lossless compression, which means there is no loss of any image detail. PNG was designed for transferring images on the Internet and not for professional-quality print graphics; therefore it does not support non-RGB color spaces such as CMYK. It supports high color and partial transparency using alpha channels.

• GIF - It uses a lossless compression which means that there is no loss in quality
  when the image is compressed. The uncompressed image stores its informatin in
  a linear fashion. Each line of pixels is read from lef to right. An interlaced GIF fie
  stores the lines of the image in a different order. Animated graphics are stored in gif
  format.
  Compatibility and appearance are the keywords on the Web. The inserted images must be
  visible and undistributed when appearing on any recipient’s device. The Web designer can
  make assumptions that the Web site will open in a computer which will have minimum
  resolution of 800x600 pixel display capability. If a mobile based Web page needs to be
  created then the specification will change.