Image Formats: What’s a JPG, GIF, PNG, SVG?

Online merchants frequently use images to convey information. Whether this is posting a product photo, a logo, adding a background image, or using an image as a link, it’s important to know which image types are available, the differences between them, and when to use each. This article will help online merchants understand the importance of image types and when to use them.

The difference in image types is due to compression. By default, most image files are large, which is not conducive to the web. The most commonly compressed image file types are JPG, GIF, PNG, and SVG.

JPG

The JPG format, short for Joint Photographic Experts Group, removes colors not visible to humans to decrease file sizes. Be careful, though. Decreasing the quality too much will lose important color information that cannot be recovered.

The JPG format allows progressive files, those that load in stages. You may have experienced an image slowly losing its blurriness and becoming clearer.

Use JPGs for product photos, human portraits, and other images where color variances are essential. Do not use JPGs for transparency, i.e., the ability to see the background. JPGs are not transparent.

GIF

A GIF — Graphics Interchange Format — reduces the number of colors to 256 from potentially thousands coming from a digital camera. GIFs also support transparency.

GIFs can display a sequence of images, similar to videos, called an animated GIF, which is a series of GIF images linked together to create motion or animation automatically.

GIFs, like JPGs, can load in segments, called interlaced GIFs. These tend to be slightly larger than regular GIFs, but they allow an image to be partially visible as it loads.

GIFs are handy for limited-color images, such as logos and graphs, or for transparency. Do not use GIFs for full-color product photos and portraits, for example, where color variances are important. Again, GIFs are limited to 256 colors.

Although the GIF is still in use, a PNG generally does nearly everything better.

PNG

PNGs — Portable Network Graphics — launched as an alternative to GIF when the latter was copyrighted and required permission to use. PNGs typically provide 5-25% greater compression than GIFs, and with a wider range of colors. PNGs also support transparency (including variable transparency, to control the degree of transparency). The downside of advanced transparency is older browsers that do not support it.

PNGs also support image interlacing, similar to GIFs, but PNGs use two-dimensional interlacing, which makes them load twice as fast as GIF images. I

SVG

SVGs — Scalable Vector Graphics — also deserve a mention. SVGs are a web standard based on XML that describes both static images and animations in two dimensions. The standard has been around for more than a decade, but it’s finally coming of age with the recent emergence of HTML5. For now, know that SVGs provide high-quality graphics and animations that do not lose detail as their size increases — from 5 pixels wide to 1,000.

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What to Use?

While there is no formula to determine the correct image type, there are some guidelines to help make an informed decision.

First, do not use a GIF if the image has many colors. PNGs or JPGs are best for wide color schemes. JPGs are best for photographs or photographic elements. PNGs are better suited for images involving text, charts, screenshots, and detailed illustrations. PNGs are best for variable transparency,

There are plenty of free alternatives that allow you to save images in different formats. Windows users can try Microsoft Paint, which lets you open an image and save it in various file formats. Mac users can try Preview. More advanced free alternatives are GIMP, for both Windows and Mac OS, and Pixelmator exclusively for Mac.