Allow images to be used as column headers

[minimav]

Prework

• [x] Read and abide by the great_tables code of conduct and contributing guidelines.
• [x] Search for duplicates among the existing issues (both open and closed).

Proposal

This can be achieved in a couple of ways already, although they both are very hacky. One is by using placeholder column names and replacing them appropriately in the HTML output created by as_raw_html with base64 encoded <img> tags (essentially the approach that is used in fmt_image).

A couple of approaches that might work for a proper implementation this:

• A .fmt_column_header_image method that mimicks fmt_image and reuses FmtImage if possible.

df = pl.DataFrame([
    {"column_name": 1.0}
])

GT(df).fmt_column_header_image(
     column_name=<path to image>,
     # fmt_image kwargs
     height=...
)

• Allow option in .col_labels to enable use of an image instead of a renaming label, or infer from argument type

df = pl.DataFrame([
    {"regular_name": 1.0, "image_column": "something"}
])

GT(df).col_labels(
    regular_name="some other name",
    # infer from Path type?
    image_column=Path(...),
)

I would be happy to try implementing something like this. Thank you 😄

[jrycw]

Thank you for bringing this issue to our attention. I'll close it now, as the vals.fmt_image() function is available to achieve the desired result.