Functional Specification of JPEG Decompression. and an Implementation for Free

JPEG is a standard for compressing images that has become very popular recently. Unlike general purpose compression algorithms, it exploits redundancy resulting from the two dimensional structure ture of pictures and from the continuous nature of photographic color images. | Functional Sp eci cation of JPEG Decompression and an Implementation for Free Jero en Fokker Department of Computer Science UtrechtUniversity P O Box TB Utrecht The Netherlands jero en cs ruu nl http www cs ruu nl jero en August Abstract A deco der for images compressed by the JPEG algorithm is stated in the pure functional programming language Gofer The program can b e regarded as a mathematical sp eci cation of the decompression algorithm the concise description which is included in full is very suitable for learning ab out the algorithm At the same time the sp eci cation is an executable program whichshows the usefulness of a functional programming language as a prototyping to ol for graphics algorithms All functions are de ned as much as p ossible at the function level i e as comp ositions of other functions A tutorial on the imp ortant concept of a State Monad whichplays an imp ortant role in the program is included From a functional programming theoretical p oint of view the new technique of currying a state monad whichisintro duced and its application in the program are interesting Intro duction JPEG is a standard for compressing images that has b ecome very p opular recently Unlike general purp ose compression algorithms it exploits redundancy resulting from the two dimensional struc ture of pictures and from the continuous nature of photographic color images Furthermore it o ers the p ossibility to let the compression lose some information whichisintended to b e hardly noticeable bythehuman viewer JPEG is named after its designer the Joint ISO and CCITT Photographic Exp ert Group In the JPEG algorithm various techniques are combined Hu man enco ding run length enco ding di erential enco ding quantization cosine transform and data reordering A general intro duction to the algorithm is given byWallace Wall in a page article It contains a numeric example which is quite instructive

TÀI LIỆU XEM NHIỀU
TỪ KHÓA LIÊN QUAN