Question about building from source: How did you get the matrix for the image?

[Alex]

I want to change the image, but I have no clue on how you got the almost 5000-line matrix of pixels.

[harrytrinh9]

You can change to your own image by convert it to bytes array, there are a lot of tools to do that.
Here's online tool powered by LVGL:
https://lvgl.io/tools/imageconverter_v9

[Noah Axon]

I personally used lcd-image-converter: https://github.com/riuson/lcd-image-converter

But @harrytrinh9 is correct, there are a lot of tools that do the same thing, and the LVGL online one looks much easier than what I did.