Sorting Out the Bitmap File Formats

Photograph of the Art College of Ontario in Toronto.
It is the final use that counts with images.

Ever since the dawn of desktop publishing, getting images into creative work has been a constant source of irritation. Toss in the web and epub  and it gets even more confusing.

Let’s take a look at the major formats and figure out use cases:

JPEG or jpg:

Developed by the Joint Photographic Experts Group  jpg only became an imaging standard in 1992, which is roughly about three years before the web gained broad acceptance.

Jpg images support up to 24-bits of color in the RGB color space. Though typically used for photos and scanned images, jpg is what is called a lossy imaging format. By that I mean every time an image undergoes jpg compression color data is lost. The amount of compression is determined at the time of creation through the use of a quality slider or value. The default value is traditionally 80% or High quality, which kicks out a rather nice result. The issues appear when you take that same image and recompress it. Suddenly colors disappear and white dots or halos appear around object. This means the color information has been wiped out in those areas and can’t be recovered. It is replaced by what is called a "specular color" .  Due to the relatively small file size, jpg has become a de facto imaging standard on the web or for any graphics displayed on a screen.

GIF

The grand daddy of web imaging formats, the Graphics Interchange Format , has been around since 1987 and was created by Compuserve partly to provide  256 colors in the Hexadecimal color space to otherwise black and white images.

The other objective behind its development was the image created had to be small enough to be transferred over  the slow dial-up modems that were common at the time. One case where the use of a GIF over a jpg image makes sense is a single-color logo or illustration being shown on a screen. Even thought the lowly GIF fell out of grace with the rise of faster bandwidth, its Animated GIF counterpart is undergoing a bit of a nostalgic renaissance.

To learn more about the lowly GIF , this article is a great overview of its history and a rather hilarious look at some of the GIF and Animated GIF files that have been created.

PNG

More commonly called “Ping” images, the Portable Network Graphic format actually rose to prominence thanks to competing GIF copyright claims between Compuserve and Unisys. The reason was due to the fact it was a non-patented alternative to GIF. Like its jpg counterpart png images use the 24-bit RGB color space. What has spurred its popularity on the web and in mobile, is the fact PNG images can also support an 8-bit Alpha channel (RGBA) which means this is the only imaging format- other than GIF- which permits transparency.

TIF

The Tagged Image File Format (TIF or TIFF) is the preferred imaging format for the print industry. The reason is this is the only format the fully supports the CMYK color space and can supports very high resolutions of 300 dpi/ppi or more. At those resolutions the file size of a tiff image, compared to its jpg or png cousins, is relatively massive. Interestingly, this format is under the control of Adobe which explains why Photoshop is the software of choice when it comes to working with TIFF images.