Compression means reducing size or cramming something into a smaller space. In computer terminology compression relates to the reduction in size of data so that one can save on space and transmission time. This can be achieved by compressing the entire transmission unit or compressing the data content.
Content compression can be done by removing all extra space characters, using a single repeat character in place of a string of repeat characters and replacing frequently occurring characters with smaller bit strings. This can reduce the file size by almost half. A program that uses a formula or algorithm works on the files and determines how to compress or decompress data. If used carefully, compression can focus on noise (unwanted disturbances in the picture) and eliminate it, thereby improving quality of the graphic while reducing size. This method of sorting out noise and signal while compressing is known as perceptually lossless compression.
Compression reduces the file size and eliminates non essential elements. But this has to be achieved without compromising on the document quality. Some programs embed images at higher resolutions than required. If size is reduced here and compressed, a lot of space can be saved. Another way to save space is use standard fonts because such fonts do not have to be embedded in the file.
Since compression of documents involves change of data bits, care has to be taken that it does not produce degraded data. There are different versions of the same compression standards available commercially. Therefore it is important to understand which works in what situation. A good way to do this is to test the fidelity of the original and compressed document using systems like OCR.
There are many advantages to compressing documents. The obvious one is the saving on storage space. Many companies today host and share their documents online and need to distribute their databases. Compression can save up to 90% of available storage space which brings down web hosting, archiving and storing costs significantly. The time required for transfer of files over the Internet or the companys own network also improves significantly.