tree aad0812426b4d36dfc068f288ace304d4e0c3780
parent 58621324090055b33290e0354847b922d8c482f2
author Vignesh Venkat <vigneshv@google.com> 1717436458 -0700
committer Vignesh Venkatasubramanian <vigneshvg@users.noreply.github.com> 1718123725 -0700

read.c: Fail if gainmap properties have more than one nclx

The current code simply adopts the first nclx property of the
gainmap item. The right behavior seems to be to fail if there are
multiple nclx properties (similar to what we do for the color image
and the tonemap image).

HEIF Section 6.5.5.1:
```
When two ColourInformationBoxes are associated with an image
item, one shall have a colour_type value of 'rICC' or 'prof'
(providing either restricted or unrestricted ICC profiles
respectively) and the other one shall have a colour_type value of
'nclx' with colour_primaries equal to 2 and
transfer_characteristics equal to 2 (2 indicating "unspecified",
since these data are supplied by the ICC profile instead).
```