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What are Portable Network Graphics?

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  • Written By: Robert Grimmick
  • Edited By: R. Halprin
  • Last Modified Date: 02 November 2016
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The term Portable Network Graphics (PNG) can refer to either the PNG image file format or images saved in the format. PNG images support a wide range of features, including lossless compression, a wide range of color support, and more advanced transparency options than its predecessors. Th Portable Network Graphics format was created as a response to patent controversies surrounding the Graphics Interchange Format (GIF). It was introduced in 1996; while the web was initially slow to support it, PNGs can be found in a variety of places both online and off.

Computer file formats are essential to our modern use of computers because they provide a standardized way for the computer to recognize what it’s supposed to do with a particular set of data. There are countless different formats including dozens of image file formats available. Some of these formats are used only in specialized fields, like professional image editing or publishing software, while others have found a wide range of uses. The PNG format, pronounced “ping,” has found acceptance in both professional and casual applications.

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The available feature set of a file format often contributes to its use; the PNG format supports a wide range of features. PNGs can be saved with a lossless compression technique, which means the file size of an image can be reduced without losing any of the image’s original quality. The compression features of PNG are so efficient that the file size is generally smaller than it would be using the GIF format. PNGs also feature more advanced transparency options than GIFs, although web browsers were slow to support this feature.

PNGs can also be saved with a different number of colors, ranging from 256 for illustrations and graphics used on the Web to truecolor images that may have as many as 16.8 million colors. The terms 8-bit PNG and 24-bit PNG, referring to the number of 1s and 0s representing each dot or pixel in an image, are sometimes used to differentiate between files with different numbers of colors. Also included in the Portable Network Graphics format are features designed to compensate for color and brightness variations between different computers and displays.

The Portable Network Graphics format was created in the mid 1990s as a response to patent controversies surrounding the compression technique used in GIF images, which were extremely popular on the web at that time. PNG was designed to be a royalty-free format and many webmasters campaigned for its adoption. The software companies that developed web browsers, however, were slow to add PNG support, and GIFs remained widely used for many years. The PNG format wasn't completely unsuccessful, however; it can now be found on web pages and in operating systems and applications where it is commonly used for icons.

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