Smallest user pictures

[pne]

I wonder what the smallest (in terms of file size) 100x100 pixel LiveJournal-legal standards-compliant (e.g. no leaving off IEND chunks from a PNG image) user picture is?

The one on this entry is 77 bytes; can anyone beat that? (Interestingly, I used netpbm to create both an all-white and an all-black image; the all-white one ended up as 82 bytes when converted to PNG with pnmtopng, 5 bytes more than the all-black one.)

And what's the smallest LiveJournal-legal user picture? I'll guess that it'll be a single-pixel picture; this user picture of mine, for example, of one black pixel, packs a whopping 67 bytes (of which 10 bytes are actual image data, i.e. the contents of the IDAT PNG chunk; the rest is checksums and headers, for an overhead of 570%!). Strangely enough, a white single pixel also takes up 67 bytes (the image data differs from that of the black pixel in three bits: it's 78 DA 63 68 00 00 00 82 00 81 in the white image and 78 DA 63 60 00 00 00 02 00 01 in the black one).