Unredacter shows you why you should never ever ever use pixelation as a redaction technique.
As mentioned in the accompanying write-up:
The bottom line is that when you need to redact text, use black bars covering the whole text. Never use anything else. No pixelization, no blurring, no fuzzing, no swirling.
unredacter (GitHub) →
Never, Ever, Ever Use Pixelation for Redacting Text →