Ever since the PDF's payload began carrying images, file size quickly became an issue. As people began adding larger and larger images into their PDF it took longer to transmit these files and the space in which they were stored filled up faster. Luckily image compression technologies were never far behind to help alleviate these problems. One such technology is JBIG2, a bi-level (black/white) image compression format introduced by the Joint Bi-level Image Experts Group. Unlike previous image compression formats (including its predecessor JBIG1) JBIG2 uses an intelligent algorithm to achieve its compression ratios. In short, the algorithm first searches for and recognizes similar groups of pixels within an image. Then, it creates symbols to represent common or repeated shapes it has found and stores them in a table. This lossless compression process does not affect image quality and the end results are documents that can be one quarter to one fifth of their original size.

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