@lennaert I'll take a look at this right now and tell you about results!
works more-more-nore faster than Sprite.ExtractImage.currentImage
behavior "Extract sprite to base64 string" by @Pode
I've just made an experiment on one of files:
Paster - about 1..1,5 seconds
ExtractImage - about 10..11 (!!!) seconds
I will use Paster for now! Thank you very much for your time and help!!
And with jsZIP plugin by @Noncentz705 I can now zip all this image data to one file and reload it any time I want
The only difference is that base64 format often has bigger weight. For example, my uploaded 53 kB JPEG converts into 300 kB PNG