"""
Tag data elements shall not partially overlap, so there shall be no part of any tag data element that falls within
the range defined for another tag in the tag table.
The tag table may contain multiple tags signatures that all reference the same tag data element offset, allowing
efficient reuse of tag data elements. In such cases, both the offset and size of the tag data elements in the tag
table shall be the same.
"""
So overlapping tag data is not allowed. Several tags referring to the exact same tag on the other hand is fine (that's what happens for the TRC tags).
Hi, thank you for this project and the blog post series – very interesting and informative!
I have a (mostly inconsequential) comment on https://photosauce.net/blog/post/making-a-minimal-srgb-icc-profile-part-1-trim-the-fat-abuse-the-spec . I couldn't find a comment feature over there, so I'm leaving an issue here. I hope that's fine.
The blog post says: "It’s perfectly legal for tag data to overlap, and in fact, for the TRC tags, it’s expected."
I'm not sure that's true. https://color.org/specification/ICC.1-2022-05.pdf says, in "7.3.1 Overview":
""" Tag data elements shall not partially overlap, so there shall be no part of any tag data element that falls within the range defined for another tag in the tag table.
The tag table may contain multiple tags signatures that all reference the same tag data element offset, allowing efficient reuse of tag data elements. In such cases, both the offset and size of the tag data elements in the tag table shall be the same. """
So overlapping tag data is not allowed. Several tags referring to the exact same tag on the other hand is fine (that's what happens for the TRC tags).
At least that's my understanding.