tree 416fe8563b5b7d4443def103e53c507338db1cff
parent b60316f4ee26ebadd29932c92706307010175f38
author John Bowler <jbowler@acm.org> 1705445942 -0800
committer John Bowler <jbowler@acm.org> 1705445942 -0800

Palette index checking fixes

The palette index checking function is called by default but only if
some *other* transformation is happening.  This makes the 'get palette
max' public API disfunctional (sometimes it works, sometimes it returns
0) and causes the supposed default behaviour of checking the palette
index only to work sometimes.  It works in pngtest, it doesn't work in
pngcp.

The check in pngread also has an off-by-one error; the number recorded
is the highest index found so it should be checked to ensure that it is
less than the palette length but it was checked for being greater.

The pull request includes a set of 8 files which all have the full range
of possible indices including one (the highest) which is invalid because
the PLTE chunk is one short of the maximum for each bit depth.

Signed-off-by: John Bowler <jbowler@acm.org>