Maybe implement a few suggestions from the comment thread to increase security. Some ideas:
Make the default pixel size value high and / or prevent low pixel size
Destroy original pixels first, take background colors from outside (the border) of the obfuscation rectangle
Generate random text as obfuscation input
Scramble sections of the obfuscation rectangle first (maybe only scramble within horizontal sections / lines to keep some resemblance of the original)
Not that you think I ignore this, I needed some time to get my new development gear up and running.
I also got a tweet about this and this is a fascinating subject, I will see what we can do about it.