CMPSC 121 Chapter Notes - Chapter 1: Lz77 And Lz78, Adobe Acrobat, Truetype
Document Summary
Limitations over ow- number is too big to be represented. Truncation- when a number is between two representable numbers. Addition: add and carry, 1+1 carry over to next digit. The number of times it occurs in the sequence. The length of the bit pattern used to represent a data item is inversely related to the frequency of the item"s use. Dictionary- collection of building blocks from which the message being compressed is constructed. Dictionary is allowed to change during the encoding process. Future occurrence as a single reference to the dictionary. For a message, divide it into a text window following a look ahead buffer. Then nd the longest segment in the text window that agrees with a pattern in the mood ahead buffer. Use a triplet to encode the segment in the look ahead buffer. Slide the window, expand the buffer, and repeat a similar process. Images- three byte per pixel~ large, unmanageable maps.
