Android Question Compress Bytes or String

[Serge Nova]

Hello everyone, I need to compress the bytes either
1. Compress the bytes directly, either
2. By converting the bytes into text and then compressing this text.
I tried this code but the text obtained by encoding64 is not compressing.

Dim org As String
    org =  su.EncodeBase64(File_To_Bytes(File.DirRootExternal, "aaaa.png"))
    
    Log($"OrgLength: ${org.Length}"$)
    '
    ' Compression
    '
    Dim compressed() As Byte = GZip.compress(org)
    Log($"CompressedBytesLength: ${compressed.Length}"$)
    Dim base64 As String = su.EncodeBase64(compressed)
    Log($"CompressedBytes converted to base64 Length: ${base64.Length}"$)

    Log($"CompressedBytes converted to base64: ${base64}"$)

    
    'Decompression
    
    Dim decompressedbytes() As Byte = su.DecodeBase64(base64)
    Log($"decompressedbytesLength: ${decompressedbytes.Length}"$)
    Dim bc As ByteConverter
    Dim uncompressed As String = bc.StringFromBytes(decompressedbytes,"UTF8")
    Log($"uncompressedLength: ${uncompressed.Length}"$)
    
    Log($"Decompressed String = ${uncompressed}"$)

Thanks in advance

 

[Brian Dean]

Why are you encoding in Base64 first? That increases the byte count by one third. Why do you not simply use GZip compression directly? And why worry about converting the bytes into text? Just compress the data using GZip.

 

[Serge Nova]

Why are you encoding in Base64 first? That increases the byte count by one third. Why do you not simply use GZip compression directly? And why worry about converting the bytes into text? Just compress the data using GZip.

Gzip only compresses strings, that's why I get the bytes from the image first, then I get the string by base64 encoding. I don't see how to directly compress a file (bytes) with GZip without encoding it first

 

[Serge Nova]

Why are you encoding in Base64 first? That increases the byte count by one third. Why do you not simply use GZip compression directly? And why worry about converting the bytes into text? Just compress the data using GZip.

If you have an example please post it.
Best regard

 

[DonManfred]

If you have an example please post it.

If you compress something (an image, pdf) ou get compressed bytes. Why you need it to convert it to a STRING? To be able you use a String you have to base64-Encode the compressed bytes.

The STRING (base64) is one third longer than just the bytes.

What you want to do with the compressed bytes? Why it is important to get a STRING?

Library LibArchiverPlus

ProBundle

ProBundle contains all the following libraries: - ArchiverPlusZip v1.13 Based on the Zip4j library, this library allows to add, extract, update and remove files from a zip archive. It supports encryption and decryption (standard and AES), Zip64 format and split zip archives. It is compatible...

www.b4x.com

 

[Erel]

Gzip only compresses strings,

That's incorrect.

 

[Brian Dean]

Gzip only compresses strings ...

What you might have heard is that zipping is usually much more effective when compressing text than when compressing images, and some images will not zip at all well. That is because zipping works by finding repeated patterns in the data. Language text contains many such patterns and compresses well. Some images with areas of block colour, like cartoons or logos, might zip well too, but landscapes with cloudy skies usually will not. That is why JPEG, rather than zipping, is more common for images.

 

[Serge Nova]

If you compress something (an image, pdf) ou get compressed bytes. Why you need it to convert it to a STRING? To be able you use a String you have to base64-Encode the compressed bytes.

So far I can't compress bytes, when I saw the CompressStrings library which only offers me string compression, I thought that since I can't compress bytes then I can convert bytes to string then compress them with GZipStrings (from CompressStrings)

What you want to do with the compressed bytes? Why it is important to get a STRING?

I want to save the files in my database as text, by directly converting the bytes of a file into text by encoding64 sometimes I get several million characters (depending on the size of this file), it is why I want:
1. Either compress the bytes (of a file) then convert them into text by the base64 encoding (regardless of the slight increase in characters due to the base64 encoding) before storing them in my database;
2. Either convert the bytes into text then compress these texts before storing them in my database

 

[Serge Nova]

That's incorrect.

I was talking about the CompressStrings library which only offers string compression, sorry for miswriting

 

[Erel]

Use CompressedStreams.CompressBytes (RandomAccessFile).

 

[Serge Nova]

What you might have heard is that zipping is usually much more effective when compressing text than when compressing images, and some images will not zip at all well. That is because zipping works by finding repeated patterns in the data. Language text contains many such patterns and compresses well. Some images with areas of block colour, like cartoons or logos, might zip well too, but landscapes with cloudy skies usually will not. That is why JPEG, rather than zipping, is more common for images.

Ok, now I understand why texts obtained from base 64 encoding do not compress.
Thank you very much for the explanation Brian Dean

 

[Serge Nova]

Use CompressedStreams.CompressBytes (RandomAccessFile).

Alright Erel, thank you very much I think that works fine for me