Tuesday, July 15, 2014

PNG Image Format

PNG stands for Portable Network Graphics. PNG is a type of image format like other image formats such as JPEG, GIF and TIFF. PNG is commonly pronounced as P-N-G where as some people also call it “ping”. PNG is used for lossless image compression and is a raster graphics file format. PNG supports all the true colors and is widely used for image transferring on World Wide Web. PNG is not suitable for printing purposes as it do no support CMYK color scheme. PNG images have a file extension PNG, or png.

History & Purpose

In the year 1995, Unisys Corporation enforced a patent on the Lempel Ziv Welch algorithm which resulted on the patent on GIF file format on the companies which uses these images for profit generation. Another drawback of GIF file format was that it could only display 256 colours while at that time graphic hardware used in computers could support much larger colour resolution. Keeping in view these drawbacks of GIF images, work on PNG started. In 1995 at a discussion on the image formats, Oliver Fromme who is the developer of famous DOS JPEG viewer QPEG, suggested the name for this new image format as PING.
Versions
Till now there have been 5 versions of PNG in total. They have been explained in the following table
Version
Release Date
Important Updates
1.0
October 1st, 1996
W3C recommended this version on the same date
1.1
December 31, 1998
Introduction of three new chunks
1.2
August 11, 1999
One Extra Chunk was added
ISO/IEC 15948:2003
November 10, 2003
PNG Became an International Standard/No chunk added.
ISO/IEC 15948:2004
March 3, 2004
Standard version for 2004

Advantages of PNG Format

  • Uses lossless image compression technique, hence no information is lost and image is retrieved keeping the same quality.
  • Supports all the true colors unlike the contemporary GIF format which only supports 256 colors.
  • Alpha channel support in PNG images allow transparency of the file format which is not possible with other file formats.

Disadvantages


  • PNG image is usually larger in size as compared to the traditional GIFF because it is a lossless image format. However if PNG is saved with 256 color scheme, its size is lesser as compared to GIF.
  • PNG format doesn’t support animations and similar graphics and for this purpose, a variation of PNG format, MNG (Multiple Network Graphics) and APNG (Animated Portable Network Graphics) are used.

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