Because Bitmap images tend to be very large, there is a need to use compression to conserve space on the hard drive. This compression is not related to any compression that you may already be using on your disk drive. There are several compression schemes that are either built into the file formats or are offered as an option when saving the file. Before we look at the individual file formats, we need to know a few things about compression and it's benefits and it's drawbacks. Compression is generaly divided into 2 categories: lossy and non-lossy Lossy compression offers the greatest amount of compression, but at a price. As the name implies, some of the image quality is lost in the process. Lossy compression schemes can reduce very large files from several MegaBytes in size to only a few KiloBytes.Most of the time, the loss in quality is not apparent. The most popular example of lossy compression is the JPEG format. Another compression method that became popular is the Wavelet compression, which also supports 24-Bit color. This file format stores Bitmap information at very high compression levels. Non-Lossy compression has been around longer than the lossy compression. It generally offers a significant amount of compression without any loss of image information (quality). Most of these compression schemes offer compression ratios between 2:1 and 4:1. the more popular versions of non-lossy compression are LZW and Packbits.