[stcredzero]

How are we to know if someone didn't just use an affine transform? This is another place where ignorance could result in security leaks.

[reaperman]

Yeah I'm not fucking around with that. Solid block of black removes the guesses. (Caveats for layered documents like PDFs).

[rudasn]

I like to convert to transparent png, cut the area I need removed, use background color (eg black) to indicate that something was removed, and export to jpg.

[stcredzero]

Programs should have explicit "secure censor" operations.