This adds APIs to get/set the two remaining new PNG-v3 colour space
chunks. The mDCV API matches that of cHRM. Both chunks support
floating point APIs (all values in the two chunks are real numbers).
Both chunks have a new encoded type, a four-digit-precision fixed-point
number, which cannot be represented in the existing `png_fixed_point`
type, so a `png_uint_32` is used.
Test examples for cICP, cLLI and mDCV are now in pngtest.png, and a
necessary change to the pngunknown.c test program has been made to
accomodate the additions.
Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
cICP was written after PLTE, not before. The other chunks were output
in an order which does not match the new PNG-v3 "priority" order.
This change outputs all chunks in the "priority" order; highest
precedence first. This means that the PNGs so written conform to
PNG v3 (cICP), and allow a streaming app to handle chunks in order,
without buffering data which may later be overridden.
Note that PNG-v3 establishes the idea of dropping ancillary chunks
which are inconveniently ordered in the definition of how APNG chunks
are handled.
This is a cherry-pick of commit 945f2602a0ea05a7938b2f52df9ef16cf3440291
from branch 'libpng18'.
Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
libpng handling of unknown chunks other than vpAg and sTER (including
unsafe-to-copy chunks which were dropped before) and eliminates the
repositioning of vpAg and sTER in pngtest.png by changing pngtest.png
(so the chunks are where libpng would put them).
