Describe the doc issue

Summary

At color conversions page, emoji command is used in section command, however its result are broken.

We have some solutions. Please could you select it ?

Related #25042

Details

In Color conversions page, emoji command is used at section command. However, its result is broken now at 4.x and 5.x .

• https://docs.opencv.org/4.9.0/de/d25/imgproc_color_conversions.html -> 4.9.0 doc is correct.
• https://docs.opencv.org/4.x/de/d25/imgproc_color_conversions.html -> 4.x doc is Broken
• https://docs.opencv.org/5.x/de/d25/imgproc_color_conversions.html -> 5.x doc is Broken

4.9.0

4.ｘ

This is doxygen limitation, it is written in here. https://www.doxygen.nl/manual/trouble.html#knowproblems

Some commands do not work inside the arguments of other commands.

e.g.

This is sample.
===============

smile is \emoji smile
-----------------------
smile is \emoji smile

And I suggest to fix arrow directions. At 4.9 and 5.x branch, they are arrow_right . However At 4.9.0 tag, Bayer to RGB is only arrow_right , otherwise are left_and_right_arrow .

Fix suggestion

We can choose one of some solutions.

Idea1 ) Using ASCII only

This idea is using ascii code to show arrow. It is easy to read in both markdown and HTML.

RGB <-> GRAY
-------------
Only ASCII

Bayer -> RGB
-------------
Only ASCII

Idea2 ) Using HTML4 character entities

This idea is using HTML4 character entities to show arrow. It is hard to read at markdown, but it looks better than idea1 at HTML.

https://www.doxygen.nl/manual/htmlcmds.html

RGB ↔ GRAY
---------------
With HTML special command

Bayer → RGB
-------------
With HTML special command

Idea3) Using math-formula

This is used at 4.9.0. But This is changed at 4.x and 5.x from 4.9 branch, so I think there are some reasons.

RGB \f$\leftrightarrow\f$ GRAY
-----------------------------------
With math formula

Bayer \f$\rightarrow\f$ RGB
-------------------------------
With math formula