You shouldn’t do it that way. There are plenty of image thumbnail controls available - check GetIt or Google it.
With respect you have a terrible habit of over-engineering everything, repeatedly. The whole point about languages like Delphi is the huge amount of well-tested and freely available components and code examples.
Instead of trying to recreate everything - and wasting huge amounts of your time and, in the process completely dominating this forum with huge discussions why don’t you instead try looking around to see if anyone has already done something similar to what you are trying to achieve? This is why Google exists - to bring the World’s information to your door. To spread existing knowledge so you can learn from it and avoid repeating every single step.
There are dozens of ready-made examples of almost everything you have asked in the past few weeks/months. It would be much better all round if you took a step back and re-examined your approach to tackling some of the tasks you’re trying to undertake. Stand on the shoulders of others to reach your goals, leverage well-worked examples and ready-made components, fulfill the “rapid” in rapid application development.
The forum is here to help - but several people are getting a little angst-ridden at the volume and extent of posts which seem to completely ignore solid practices like using Google and adapting ready-made examples, libraries, and components to fit.
Trying to write a component from scratch which displays image lists in a TPanel (which a TScrollBox or other container would be more appropriate anyway) when it is one of the most common examples of code there is a typical instance of what I mean. Did you even look to see if it had been done before? I even showed such a thing in my recent webinar on the TFrameView components - and it was so common a type of use case I didn’t even need to comment on the fact I was showing images in the way you describe because everyone will have seen that kind of thing dozens of times before if they had spent even 20 minutes on researching it.
There are Skia examples, TScrollbox examples, VCL examples, and FireMonkey examples that do this. I first wrote that kind of control in the late 1990s and displayed images and fonts in it.
Google for examples, try them out, then ask better, more succinct questions. Resist the temptation to reinvent everything from scratch and look for something which either does what you want or can be adapted. Then, when you ask questions here you will get a much more positive and engaged response with a greater likelihood of people joining in the conversation.
I say all this with all the possible affection for you and your journey in software development.
