[phkahler]

Ultimately it's going to require a malloc to get the space for all those pixels. That is where things should fail. If not, how is one to specify what the image size limits should be? Ever try to open the Blue Marble images from NASA? In a web browser? Back in 2001?

[to3m]

Any decent library (of any sort) should already be providing hooks for its memory allocation. This isn't necessarily provided as a security feature, and it's common for your callbacks not to get much in the way of information about what's going on, but it will allow you to at least crudely put a cap on the library's memory usage.