Why was the PNG file format created

PNG (.png)

PNG (pronounced ping) stands for Portable Network Graphics and is a format for graphics and images on websites. The greatest advantage of saving photos in PNG format over JPEG is lossless compression. The advantage over GIF is that PNG graphics can be created without paying license fees.
PNG combines the advantages of GIF and JPEG files. Furthermore, PNG files can contain transparency information (allow transparent parts of the image), either in the form of an alpha channel or for each color of the color palette. An alpha channel is additional information that specifies for each pixel how much of the background of the image should shine through.

PNG graphics can have a color depth of up to 16.7 million colors and store transparency information (i.e. allow parts of the image to be transparent).
PNG is mainly designed for use in data networks.

Disadvantage:

  • no animations
  • not supported by some browsers
  • higher computing time with compression
  • less complex than TIFF format

The file size is sometimes significantly larger than that of JPEG, which is why PNG is the successor to the GIF format. Due to the large file size, PNG formats cannot be viewed in older browsers.

Like GIF, PNG can process pixels from a color palette with up to 256 entries. In addition, it is possible to save grayscale images with 1, 2, 4, 8 or 16 bits and color images (RGB) with 8 or 16 bits per channel (i.e. 24 or 48 bits per pixel).
PNG was deliberately designed without animation capability as with GIF, since a separate format (MNG) was to be developed for this. The two formats were supposed to replace GIF, but so far it hasn't.
PNG supports alpha channels of 8 or 16 bit, which corresponds to 256 or 65536 levels of transparency.
PNG supports metadata, which can contain more information about the image, such as color correction.

Examples:

Example 1: PNG file with alpha channel, can be displayed on any background

Example 2: PNG file of the same image, on a different background.

Despite the many advantages, the PNG could not prevail over GIF or JPEG.

Credentials:

http://goethe.ira.uka.de/seminare/redundanz/vortrag12/#gedacht

http://www.gif-bilder.de/lexikon/png.html

http://de.wikipedia.org/wiki/Portable_Network_Graphics

http://www.drweb.de/magazin/was-ist-png/

http://de.kioskea.net/contents/video/format-png.php3

J. Boehringer / P. B├╝hler / P. Schlaich, Compendium of media design for digital and print media, Berlin Heidelberg, 2006.