The only cap was 64 MiB of input, and a decode bomb is a small file. A
20000x20000 PNG of flat colour compresses to a few hundred kilobytes,
decodes to 400 million pixels, and flattenAndScale then allocated a
second buffer of the same dimensions before scaling anything. That is
3.2 GB of live heap from one request, on a laptop, in the process that
owns the database and the socket, and max_dim never got a chance to
help. The header is read first now and a source over forty megapixels is
refused. The scaler reads the source through At and allocates only the
destination, so flattening no longer doubles the peak.
Found in review of #72.
kami
61ba58388f