What Is PNG?

Date First Published: 28th July 2023

Topic: Computer Systems

Subtopic: Computer Software

Article Type: Computer Terms & Definitions

Difficulty Level: 5/10

Learn about what PNG is in this article.

Stands for Portable Network Graphics. PNG is an image format that uses lossless compression to save high-quality images in a low file size. It also supports transparency and different colour depths that can go as high as 32-bit. This makes it suitable for sharing complex web graphics, images, and photographs on the web that require transparency. PNG is one of the most common image formats along with JPEG, GIF, SVG, and BMP.

PNG files can be opened by most image viewers, video viewers, and web browsers. Windows and macOS come with built-in image viewers that support PNG files, including Microsoft Photos and Apple Preview. Most image editors, including Microsoft Paint and Corel PaintShop Pro, can also convert PNG files to other image formats.

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PNG files have the ".png" file extension and the "image/png" MIME media type.

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The 8 bits above 24-bit are used to store levels of transparency in the image.

Note:

The acronym PNG is sometimes unofficially called the recursive acronym "PNG's not GIF."

Difference Between PNG and JPEG

PNG and JPEG are the two most widely used image formats on the web, but there are some differences between them. The main difference between a PNG and JPEG file is the loss of quality. Since PNG uses lossless compression, saving it does not reduce its quality or cause it to lose any original file data when compressed. Due to the different compression processes, PNG files contain more data than JPEG files, take up more space, and load slower on the web than JPEGs. Unlike JPEGs, PNGs also support transparent backgrounds, making them more suitable for graphic design, logos, and pictures with text.

History

The first PNG draft was issued on 4th January 1995. A week later, most of the PNG features had been proposed and accepted. The group produced seven important drafts over the next three weeks. By the beginning of March 1995, all the specifications were in place and accepted.

PNG was introduced on 10th January 1996 as an improved and non-patented replacement for the GIF format. Since the GIF format was a patented format owned by Unisys, web users could freely make, send, and view GIF files, but any software that created and displayed GIF files required licensing fees to be paid to Unisys.

The PNG format also supported more colours than the GIF format. The GIF format only supported fully opaque or fully transparent pixels, whilst PNG images include 8 bits for transparency. The format also supports full-colour, non-indexed RGB or RGBA images and grayscale images.

The full specification of the PNG was released on 1st October 1996 and approved by the W3C. On 31st December 1998, the specification was revised to version 1.1, which fixed technical issues for gamma and colour correction. Although GIF supports animation, it was decided that PNG should be a single-image format.

Two animated versions of the PNG format exist. In 2001, the developers of PNG released the Multiple-image Network Graphics (MNG) format, with support for animation. It failed to achieve enough support amongst major web browsers and was rarely used by website publishers. In 2008, Mozilla developers with similar goals released the Animated Portable Network Graphics (APNG). Although it is less common than the GIF format, it is commonly used for thumbnails on Sony's PlayStation Portable system and has been supported by Chromium-based browsers since 2017.

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