Digital Images: Differentiating between Jpeg, GIF and Png

The internet has gracefully melted into Maslow’s hierarchy of needs. It’s become a source of information, socialisation, self-actualization and many of us depend on it for our income or employment. Much of what we do online involves the use of images. Understanding the difference between uploading a Jpeg or a Png and how a GIF works, might come in handy if you are looking to increase your web-efficiency.


Joint Photographic Experts Group (1986)

This is the standard format used by most digital cameras – the file extension is either .jpg or .jpeg and displays millions of colours in a 16-bit data format. JPEG is compatible with most platforms (such as PC or Mac) and programmes, such as browsers and image editors. This format used a complex compression algorithm. 60% – 75% is optimal for web use, during compression; colour detail is sacrificed in order to save space. This also means that JPEGs have a much faster upload time than other formats.

JPEG is best used for still images, photographs, complex colouring of images and light and dark shading on an image.


Graphics Interchange Format (1987)

Believe it or not, file extension .GIF was originally invented to transfer images quicker over slow internet connections. This format uses a process which combines two pixel colours in order to make one colour (known as dithering), meaning the format only really uses 256 indexed colours, additionally it also has the option of using single-bit transparency, so that only one colour can be transparent. Using fewer colours means that GIFs can be compressed even smaller than JPEGs and the compression does not lose any data (lossless compression). One of the more exciting aspects of this format is that it can be interlaced – using progressive loading whereby you initially view a low-quality version of an image and gradually more detail is added as the image loads.

GIFs can be used for animations (as avid 9Gagers will know), small icons, web graphics with few colours and for simple images such as line drawings or simple cartoons.

There is a debate about how to pronounce this file extension’s name, but inventor Steve Wilhite always pronounces it as ‘jif’.


Portable Network Graphics (mid -90’s)

This format offers only the best aspects of both the JPEG and GIF formats. There are two options to choose from when it comes to .PNG: PNG-8 and PNG-24. The former is similar to the GIF, using 1-bit transparency and only 256 colours, however when compressed, this file is even smaller than a GIF. The latter, PNG-24, is similar to .JPEG, using 24-bit colour but it also uses lossless compression, meaning that these two aspects combined will compress a file larger than a JPEG. PNG also uses alpha channels, meaning the transparency of the background can be set, but there will be some older browsers which does not support these alpha channels.

This format is best used for web images (especially logos), images in the editing process and complex photographs.


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