How to compress(reduce a zip file size from 2 mb to 300kb) .zip file in C#

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string path = createzip(txtnum.Text.ToString());
DirectoryInfo dir = new DirectoryInfo(path);
FileInfo[] zip = dir.GetFiles("*.zip");
if (zip[0].FullName != null)
{
using (FileStream target = new FileStream(zip[0].FullName, FileMode.Create, FileAccess.Write))
using (GZipStream alg = new GZipStream(target, CompressionMode.Compress))
{
byte[] data = File.ReadAllBytes(zip[0].FullName);
alg.Write(data, 0, data.Length);
alg.Flush();

}
}

Posted 8-Jan-15 0:40am

sheena k

Updated 8-Jan-15 0:41am

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Praveen Kumar Upadhyay 8-Jan-15 6:44am

What is your question?

sheena k 8-Jan-15 6:52am

how to reduce the .zip file size ???
right now its size in MB I want to reduce it into KB...can u help me ??

Richard MacCutchan 8-Jan-15 7:01am

You cannot reduce its size; it is already compressed.

sheena k 8-Jan-15 7:04am

@Richard : yes its already compressed but little bit difference coming by using this way....I want another method to reduce file upto 70%

Richard MacCutchan 8-Jan-15 7:10am

What part of "You cannot reduce its size; it is already compressed." do you not understand? If the data is compressed then you cannot compress it any more.

sheena k 8-Jan-15 7:39am

I tried by this method but very less difference(that is not acceptable).i want to apply another method becoz I want to compress file size from 2 mb to 300 kb.

Richard MacCutchan 8-Jan-15 7:52am

I don't know whether it is a language problem or you are just being obtuse, but I repeat: You cannot compress data that is already compressed.

Arjsrya 8-Jan-15 7:02am

What is the size of file before and after compression?

sheena k 8-Jan-15 7:09am

before compression: 2295KB
after compression: 2232KB

Arjsrya 8-Jan-15 7:12am

Have you tried to compress files directly using 7-zip or winrar.is it reducing the file size to KBs?

sheena k 8-Jan-15 7:18am

no

Arjsrya 8-Jan-15 7:29am

then try and tell us.

What is the size after compression when doing from coding?
What is the size after compression when doing manually from winrar or zip?

lukeer 8-Jan-15 7:30am

See? That doesn't work.

What are the original files? Is there a chance to get them smaller before your compression? That means: are you in control of the files, or does the user select anything he wants?

sheena k 8-Jan-15 8:29am

thanks to all...u people are correct.
Online converter also unable to do compress this file.

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OriginalGriff · Answer 1 · 2015-01-08T01:01:00

You can't, not necessarily - it depends on what the file holds how much it can be compressed without losing data. Some file formats compress well: XLSX files for example are XML (largely text) based and tend to compress well, while AVI files are already compressed and there isn't a lot you can do.

Certainly, you can't guarantee to compress "any file" by any amount - and some files may get larger after compression as a result of the overheads of compression!

But if it can be done, then look at SharpZipLib[^] or similar.

BillWoodruff · Answer 2 · 2015-01-08T05:26:00

I suggest you study the difference between "losless compression" and "lossy compression," and get clear which one you want to use in a given situation.

And, be aware that a given file has a certain limit to how much it can be compressed losslessly by any specific method of compression (Zip, WinRar, 7-Zip, etc.): I have seen some files that losslessly compressed by a factor of 25% smaller in WinRar than with Zip, and other files that had only slight differences.

If the file is encoded, encrypted, natively compressed (as are bitmap files in general ... .jpg, .png, etc., and audio, and vidoe files, etc.) then further compression is usually useless.

.flac is an example of a music file format which is lossless, but still can compress to some degree.

.jpg is, of course, a lossy compression method, with the compression factor a variable you can set. .png is lossless, except that by altering the bit-depth of the color-palette you can change the size of the file: of course, if you lower the bit-depth of the palette you will potentially lose color information.

How to compress(reduce a zip file size from 2 mb to 300kb) .zip file in C#

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