How do I print characters that are not defined in UTF-8 as "images"?

I am developing an application called Zinnia-Tomoe that allows iOS devices to input and output kanji using a license-free handwriting recognition engine.
You can think of Zinnia as an online input application that can recognize symbols and other pen strokes, and Tomoe as a character output application that uses Zinnia's functions to input Japanese kanji and simplified Chinese offline.

What I want to do is input and output a large number of characters that are not defined in UTF-8 as non-Chinese characters as images.

Tomoe has the ability to arrange a list of coordinates called "S" in a certain order to eventually form a kanji stroke.

Disclose some of the S expressions.

(character(value1)(width1000)(height1000)(strokes(75464)(923468)))
(character(value)(width1000)(height1000)(strokes(93198)(913205))(495203)(470847)(405784)))

In this way, it consists of a list of characters you want to print and numbers indicating coordinates, and eventually recognizes kanji by handwriting by following the coordinates.

However, UTF-8 is struggling to use undefined non-Chinese characters as new characters in the app, and I want to avoid the problem by using them as images as a means of doing so, but this doesn't work very well.

For example, UTF-8 does not define characters consisting of only the first to third images of the kanji characters "Yu" or "Liu.""Therefore, of course, this ""non-Chinese characters"" can not be printed on this bulletin board, so in order to avoid that, we will save this ""non-Chinese characters"" as the image file ""img0001.jpg"" and so on, and then

(character(value Image("img0001")(width1000)(height1000)…(omitted below)

It was defined as follows:However, the conversion candidate will only display the first and second letters of Image("img0001") and will not function properly.
I forgot to mention that each candidate for conversion of multiple kanji characters should display only two half-width alphanumeric characters or one full-width character.

Then I thought of letting them choose a candidate for "image" in the switch statement, but it is unclear whether this will work or not.

I still have some alternatives in my mind, but I want to finish them as simple as possible.So I am writing to ask for your advice.
The main development language of Zinnia-Tomoe itself is Objective-C, but in this question, the language should be Swift and the framework should be SwiftUI if possible.