I've been using Open Stage Control for a little bit now and I have to agree with everyone else - it's awesome!
By way of a shameless plug for my own content, I have been sharing on YouTube a tutorial series on how to use Open Stage Control and the theme of the tutorial series is creating a Behringer BCF2000 in software.
This is a creative and excellent tutorial on how to approach custom fader graphics.
I had looked into the source code approach, but for the same reasons as you I concluded that wasn't going to be a good long term approach.
On a different note, I noticed in the video that you're not using MCU mode. I went back and forth on using my BCF2000 in MCU mode and user mode, and ended up mostly using MCU mode in the end. If you ever consider going in that direction, it might be helpful to know that jean-emmanuel has a good MCU emulator using OSC also on github.
There are at least to ways to skin the cat. One is to rotate the image, the other uses image strips (e.g. generated by knobman).
I really like mackmusic's idea to use the html property of the widget, will give it a try.
I used a different approach. I put an "invisible" (alpha=0) knob widget on top of an image. The image is rotated in accordance to the knob position. The following code goes into the css property of the image widget:
hey @jean-emmanuel - really cool to hear from you directly. awesome tool you have created! the videos are more popular than i had initially expected. seems there is not too much out there. and i'm so glad you like the content - i did wonder what you might think! it's not very advanced what i am doing (i will cover more difficult stuff soon hopefully) but i wanted to show more what can be done visually but still keep the original source code.
i'm not on this forum very often so apologies to others if i have not replied to you. it' easier to get me through the YT comments if you want to interact directly, or also on discord (links in the videos).