programming-for-dummies

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Lossy Data Compression
IAMSAMSAMIAM#
Scans “I” and stores it in the dictionary
IAMSAMSAMIAM#
Scans “A” and stores it in the dictionary
IAMSAMSAMIAM#
1 A
9 I
13 M
19 S
27 AM
28 SA
29 MI
30 AM#
Scans “M” and stores it in the dictionary
IAMSAMSAMIAM#
Scans “S” and stores it in the dictionary
IAMSAMSAMIAM#
Scans “A”, which is already in the dictionary,
so it scans the next two characters “AM”
IAMSAMSAMIAM#
Figure 4-4:
The LZW
algorithm
stores
increasing
larger
strings as
numbers.
Scans “S”, which is already in the dictionary,
so it scans the next two characters “SA”
IAMSAMSAMIAM#
Scans “M”, which is already in the dictionary,
so it scans the next two characters “MI”
IAMSAMSAMIAM#
Scans “A”and “AM”, which is already in the dictionary,
so it scans the next three characters “AM#”
Lossy Data Compression
Lossy data compression shrinks data through a combination of packing data
more efficiently (like lossless compression) and by throwing out chunks of
data that aren’t considered crucial. As a result, lossy compression is used
less often for text (where losing data is unacceptable because a single missing
word or number can alter the entire meaning of the text) and more often
for audio, graphics, and video.