[doc] Blob compression

[Erik Mueller-Harder]

Hi, Ruslan --

The Valentina Database Kernel documentation (page 27) says this about the VBlob class:

• On default Valentina uses ZIP compression.
• You can set up level of compression in range 0..9.
    0 - fastest compression.
    9 - best compression.

I know how to turn compression on and off with the "compressed" property, but I don't see how to change the compression level.

I do see that VPictures have a "quality" compression parameter of 0 to 100, but I'm storing text in a VText subclass of VBlob, not (of course!) in VPicture.

Are there levels of compression for the VText subclass of VBlob?  How does one access it?  What's the default?  Is it merely a case of speed versus degree of compression?

Thanks for your clarification,

Erik