subject: PDF Files Compression Method [print this page] PDF Files Compression Method PDF Files Compression Method
You would not believe but Portable Document Format can be really compact in size as compared to PostScript that could be seen quite capable in reducing its size. This is a format that is used by a lot by people and they convert documents into pdf from word. This is possible with a better and organized structure for data but all the more the ability to compress the data so well is only because of algorithms that could be utilized. Some need to convert their pdf documents to word in order to edit the pdf files and use document conversion software for converting pdf to word. In fact is utilized extensively all through the world. The followings are:
CCITT G3/G4 is used for monochrome imageries
LZW- This gets replaced by Flate since this too is utilized to compress text and images that are present in your file as data.
RLE- This is again used for monochrome images.
ZIP- This is used for color and grayscale pictures or images.
JPEG- This is a lossy algorithm that is brought into usage for pictures.
JPEG G2000- This is even a better and modern alternative to the other which is used for compression of files.
Flate- This is mainly used so as to reduce the size of text plus images in a file.
JBIG2- This one is an alternative to CCITT compression for monochrome imageries.
How the method works?
Supposedly if you make use of Acrobat Distiller, this would decompress all of the images in a PostScript file and subsequently compress them once more when creating a pdf file.
How you could test the compression that was utilized in such a file?
In a few cases, opening such a file with the help of a text editor could handle binary data and then search Filter keywords
Compression algorithms usage: CCITT compression could be used for black and white images. The method is similar to the one used in fax devices. The quality of images is not lost during the procedure when carried out. Acrobat provides group 3 or 4 compression and most of the people support the fact that group 4 is better to be used.
Flate compression- This is a really complex compression algorithm. As said before, JBIG2 is an alternative to CCITT compression for monochrome classic version of images. JPEG compression is utilized for hued and grayscale images and could range from lossy to non-lossy edition. In Acrobat you'd find lossy JPEG compression and the better the ratio the more chances of losing details.
