How does image/PDF File compression work?
In: Technology
There are two general types of data compression: lossy and lossless.
Lossless simply rearranges data in order to reduce size. Instead of saying WWW you say 3W. So basically find repeated patterns and replace them with a shorthand.
Lossy data compression depends on the medium. For a picture you can for example not save every pixel, but only the average of 4 pixels together. That way it becomes more blurry and pixelated but you can reduce size by factor 4.
Often you can restore parts of lossy compression by making educated guesses wich data was deleted.
There are pretty dedicated tactics that try to reduce size by only keeping the details that humans notice. This kind of requires the knowledge what kind of information people are able to grasp and wich not, so it’s still something currently researched.
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