What is a PNG file?

Lewis Wake
Wednesday 12 January 2022

You know what a JPEG and a GIF is, but what is a PNG file?

What does PNG stand for?

PNG officially stands for Portable Network Graphics.

What is a PNG file?

Portable Network Graphics is a raster-graphics file format that supports lossless data compression.

The PNG format was designed for transferring images on the internet with lossless data compression and is the most frequently used uncompressed raster image format on the internet.

In addition to that, PNG files are capable of containing 24-bit RGB colour palettes and greyscale images, with or without an alpha channel transparency.

This lossless data compression format was created to replace the Graphics Interchange Format (GIF) as it has a wider range of colour depths. GIF is limited to 8-bit indexed colours while PNG can use 24-bit and 48-bit true colour.

Like GIF images, PNG also has the ability to display transparent backgrounds.

When was the PNG created?

The PNG format was first developed in 1995.

The data compression algorithm used in GIFs was patented by Unisys. This patent required all software supporting GIF files pay royalties to Unisys. This sparked a group of developers to devise a free alternative format.

Because of this, PNG unofficially stands for “PNG’s Not GIF“.

The goals for the PNG project were:

  1. To make it portable, not just across platforms and operating systems, but also across implementations
  2. To make it network-friendly
  3. To create a new graphics format capable of replacing GIF.

Is a PNG better than JPEG?

The biggest advantage of PNG over JPEG is that the compression is lossless, meaning there is no loss in quality each time it is opened and saved again.

JPEG produces visual artifacts around high-contrast areas.

JPEG format images can produce smaller file sizes than PNG for photographic images. JPEG is specifically designed for photographic image data which is typically dominated by soft, low-contrast transitions, and an amount of noise or similar irregular structures. Using PNG instead of a high-quality JPEG for such images would result in a large increase in filesize with negligible gain in quality.

In comparison, when storing images that contain text, line art, or graphics – images with sharp transitions and large areas of solid colour – the PNG format can compress image data more than JPEG can.

When should you use a PNG?

PNG is a type of image that is used in web design and creative projects. It allows an object to be placed into software with a clear background, or as a partially transparent image.

PNG files are good for sharing icons, logos, and graphics at a low file size. They are typically used for app icons, favicons on websites, and chart graphics.

PNG files are preferred for sharing photographic images with a transparent background. This is typically shown to be overlaid onto a checkered background to indicate transparency.

Due to the high file size, it is not advised to share a photograph as a PNG file format.

Kittens on a transparent grid background
A PNG image with an 8-bit transparency channel overlaid onto a checkered background, typically used in graphics software to indicate transparency

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