This week I found the concepts of lossless compression and lossy compression difficult to understand. The way the instructor described it: lossless compression was “not throwing away data, just eliminating redundancy in the image to save space” and lossy compression, which is more widely used, “discards some data, but only nondiscernable data (to the majority of people).” Lossless compression is used for archiving original works, in order to be able to edit them later. Lossy compression is used for “delivering, it’s the ideal jpeg.” Unfortunately, I couldn’t understand how eliminating redundancy in an image doesn’t distort the image, and how that doesn’t count as throwing away data. I also don’t understand how some people can discern the data that was discarded in lossy compression, while the majority of people cannot tell.
After further research, I have found that lossless data compression allows the original data to be compressed and reconstructed the exact same, whereas lossy compression only allows an approximation of the original data to be reconstructed. A lossy compression technique can reduce the space needed by a greater amount than lossless compression, however only certain types of data (i.e. graphics, audio, and video) can tolerate lossy compression. Data and programs must be compressed with the lossless technique. In a scanned photograph, the sky is many different pixels of blue, but in lossy compression, the program picks one color of blue to be used for every pixel.
If you are still confused, or desire further information on the topic, I found http://computer.howstuffworks.com/file-compression3.htm extremely helpful.
References:
http://www.webopedia.com/TERM/L/lossless_compression.html
http://en.wikipedia.org/wiki/Lossless_data_compression
After further research, I have found that lossless data compression allows the original data to be compressed and reconstructed the exact same, whereas lossy compression only allows an approximation of the original data to be reconstructed. A lossy compression technique can reduce the space needed by a greater amount than lossless compression, however only certain types of data (i.e. graphics, audio, and video) can tolerate lossy compression. Data and programs must be compressed with the lossless technique. In a scanned photograph, the sky is many different pixels of blue, but in lossy compression, the program picks one color of blue to be used for every pixel.
If you are still confused, or desire further information on the topic, I found http://computer.howstuffworks.com/file-compression3.htm extremely helpful.
References:
http://www.webopedia.com/TERM/L/lossless_compression.html
http://en.wikipedia.org/wiki/Lossless_data_compression
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