Portable Network Graphics (PNG) is an unpatented file format that supports lossless data compression and transparent backgrounds, and is frequently used on the web.
The PNG file format is designed as a lossless format intended for use with web graphics – particularly those with a transparent background. The PNG format is not patented, meaning any image or graphic editing software can work with PNGs without licensing the right to do so. As a result, the PNG format is the most widely used lossless image compression format on the web.
Images and graphic files stored in PNG format include the file extension “.png” and are sometimes referred to as ping files.
Frequently Asked Questions
What does it mean that PNGs support lossless data compression?
Images and graphics used on the web are often compressed to make them easier to work with and transfer. File formats that can be compressed and later decompressed without the loss of any data are referred to as lossless. File formats that achieve compression by deleting data are referred to as lossy. PNGs are lossless, meaning that they can be compressed without the loss of any data. JPEGs, another common file format used for pictures on the web, require less disk space, but are lossy and image quality is reduced when images are compressed.
When was the PNG file format developed?
The PNG file format was developed as an alternative to the proprietary GIF file format. In 1995, a discussions took place on the Usenet group “comp.graphics”. The content of that discussion was largely the basis for the development of the open-source PNG format.
Replacement of the GIF format was desirable for at least two reasons. First, Unisys owned the patent on the GIF format and creating software to work with GIFs required the negotiation of a licensing agreement with Unisys. Second, at the time, GIF could only support 265 colors while computers were capable of displaying many additional colors. Correction of these two obstacles was a driving force behind development of the PNG format.
Where are PNGs used today?
PNGs are used extensively on the web in particular as a format for graphics with a transparent background. Support for transparent backgrounds means that PNGs can be layered over other images or colors to create unique custom effects.
When should a PNG not be used?
PNGs are not the best choice when selecting a file format for storing large image files since PNG files require considerably more disk space than the same image stored in JPEG format. PNGs were designed for use transferring images for the web and do not support non-RGB color models, such as CMYK, meaning that PNGs should not be used for graphics intended for professional-quality printing.
What's the difference between a PNG and a JPEG?
While PNGs support lossless compression and transparent backgrounds, JPEGs (or JPGs) are lossy and cannot have transparent backgrounds. However, JPEGs require significantly less disk space than PNGs, making JPEG an ideal format for high-resolution photographs.