Image Compression and Artifacting

Image compression, in it's lossy form, sucks ass. Now that that's off my chest, I'll tell you why.

Data compression isn't a new science - it's been around for almost as long as computers have. The need to fit more and more data into a smaller and smaller space is efficient and convenient for a number of reasons.

There are many different ways to compress data on a computer. You've almost certainly run across them before - ZIP, LZH, ARC, ZOO, ACE, and many others, are all compression standards. Some are more effective than others, and some are more useful on certain kinds of data.

When computers became powerful enough to display more than sixteen colours, we started seeing pictures on our screens. Larger, and larger, to the point where some pictures were too large to fit on a floppy.

Something, obviously, had to be done. Enter compression.

The first format to gain widespread acceptance was CompuServe's GIF (Graphic Interchange Format) standard. Soon, however, the GIF limitations crept up on us. It was designed with 8-bit graphics in mind, so it was limited to 256 colours. As our computers started increasing in power, we had 512, 4,096, and all the way up to sixteen million colours.

Something, obviously, had to be done. Enter JPG.

The JPG format was designed by the Joint Picture Experts Group. I dunno who they were, but they did the work. It allowed for sixteen million colours - and differed in one major way from GIF.

It was a lossy compression. It used perceptual encoding in it's compression duties to toss out any data it deemed irrelevant or unseen. It was amazing - it allowed for varying degrees of compression and made the already small GIF file size even smaller. A lot smaller. But it was evil. It was evil to it's binary little core - it made your pictures look CRAPPY!

Any 'fuzz' or 'crap' introduced into an image or video sequence by the compression algorithm is called an ARTIFACT. The appearance of artifacts in an image is (to me) distracting and irritating.

At least, it could. That's the basic theory, here's the basic proof. In order to be useful, the JPG compression needed to be cranked up to conserve a significant amount of space. This is what results when you compress a GIF (Which is lossless - it loses no information during compression) into a JPG at varying rates of compression.
Compression & Artifacting...
Black & White Examples...
Colour Examples...

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