> But if you transform the image into a format that doesn‘t have PNG’s complexity (in a low-privilege process, of course), the malicious nature of the PNG ‘should’ be eliminated and then safe for parsing at a higher privilege level. Even if the attacker manages to compromise the low-privilege process with a malicious PNG, the high-privilege process will only parse the compromised process' output with a simple, plausibly-safe parser.

It's interesting to get a sense of how deeply unrealistic they think it is, to write a safe parser for a typical data format in an unsafe language.