Symbol Representation in Map Image Compression UNIVERSITY OF JOENSUU DEPARTMENT OF COMPUTER SCIENCE FINLAND Alexander Akimov and Pasi Fränti ACM Symposium on Applied Computing (SAC’04) March 2004, Nicosia, Cyprus
Application of map images
Server side Operations: Rasterization Compression Benefits: Independent on vector formats Large map databases at server side Low cost client side applications
Client side = + Operations: Decompression Viewing
Map image compression
Text rasterization Hershey vector font (0,0)+(5,10)+(8,0)+(–1, –1) + (2,5)+ (6,5) =
Text rotation Text is stored as bitmaps: Same text after rotation consists from different bitmaps
Text rotation process
Text control data
MISS file structure
Text layer
Decoding Generic region decoding Text region decoding 1.Decoding of symbols bitmaps 2.Decoding of control data
Experimental results
Statistical data of the text rasterization Size of dictionary Number of symbols Size of compressed blocks Strip data X sizes Y sizes Strip lengths X coordinates Y coordinates Bitmap’s indexes
Conclusions Improved map image compression... but where was the intelligence, computational logic, or image analysis? Intelligence was that we avoided all AI and IA operations at the client side.