> On Mac OS X, I get 8 tests failing:
>
> test[1|2|4|8]Bit
> test[1|2|4|8]BitReversed
>
> The assertion that fails is "original bits = decoded bits".  In every
> case, the original has a bunch of bits all with the same non-zero value
> where the decoded bits are zero.

Ah, byte-sex issues. Hm ... let's see, maybe changing the following in
PNGReadWriter>>copyPixelsIndexed: may help.

Line 3:
hack := Form extent: width at 1 depth: form depth negated bits: scanline.

Remove the "negated" in the above and see if that works for you.
Alternatively see if removing the swizzleHack in this method changes
anything.

Cheers,
  - Andreas