How the files are compressed ?
Using the file compression is a normal process for our computing needs , whether in the case of data transmission or data storage . Even the layman in computing know how to zip a file and unzip it . But what happens when you compress a file , how the file size of the original file reduced and still you can un compress it and restore all the data ? Hope we can have a basic discussion on it .
When I tried to compress my word file , it compresses well and file size reduced to a considerable amount and when I try to compress my jpg file , it does not reduced much and in some cases the size of the file increased a bit , why it is so ?
hope it is your question . Why the jpeg file is not responding well to file compression software is because it is already a compressed format. If you try to compress further , actually the size will be increased due to certain overhead associated with it .
Suppose you have a text file with you , and you found out that the word ” Computer ” is repeated 30 times in that text file . So the word is redundantly used 29 times . Why can not we use a procedure so that when ever the word Computer is repeated a pointer is used to indicate that this word is a repeating from the first line of the text . The example we mentioned is the basic idea behind the loss-less file compression . ie we will observe a binary string in the file and when ever that string is repeated a pointer is used to mention that this string is used previously , there by saving the space needed to save that bits . Wen we are uncompressing the file , the reverse process happens and the file will be available intact .
But the case of your Jpeg file is little bit different. Jpeg is a compressed file format . It uses a Lossy file compression procedure . ie it compresses a file based on some assumption about the picture details and reducing the unnoticed , unwanted elements to reduce the size . The same thing happens with your mp3 , mp4 formats and many video compression technologies .
So a well compressed file does not have any redundant information on it as all of them are removed during the process if compression , it does not make sense to run your compression program again on it .