[londons_explore]

If checksum calculation was any substantial portion of image decoding, I think that would be a strong case for simply not checking the checksum.

If you put corrupted data into a PNG decoder, I don't think it's awfully important to most users whether they get a decode error or a garbled image out.

[wooosh]

This was actually considered, and other libraries do ignore checksums, or at least have options to:

https://github.com/richgel999/fpng/issues/9