Thanks for explaining, from a user perspective the best thing to do is definitely graceful recovery, but bugs like this highlight that there's value to the ecos

Thanks for explaining, from a user perspective the best thing to do is definitely graceful recovery, but bugs like this highlight that there's value to the ecosystem in failing loudly whenever anything is out of spec. The appropriate balance of those behaviors is obviously a function of the nature of the ecosystem, and could be different for different tools. I'd suggest that for PNG in particular, one reasonable behavior would be to show a little red "File corrupted!" warning or popup for these sort of out-of-spec-but-probably-recoverable issues, which would probably have been noticed and filed as a bug for the developers of these tools, even if only a small fraction of viewers had that behavior. Something like a thumbnail viewer should maybe just opt to early-abort whenever anything sketchy is going on, especially since out-of-spec behaviors can lead to security issues.