Let me explain. I saw videos on YT, where some guys found the seed of the old title screen of the minecraft, the seed of some paintings and the seed of the world shown in the default resource pack image. I heard that it is very hard and they used clouds, flowers, trees, mountains to determine the position of the part of the world shown in the image. I want to try, I know it is difficile, but in my case would be easier because an youtuber recording minecraft doesn't want to tell his world's seed and it is kind of annoying. The guys that found the seeds for the words I just mentioned had only an image, or a panoramic image, but I this youtuber has hours of recordings, walking, exploring that world and I ca check for cloud patterns and things useful, and maybe easier in this case. However, I don't know where to start since I know nothing about minecraft terrain generation. If you know anything about how to find a seed. I mention that I worked before with my own procedural terrain generation for my "game"mini projects in java, rendered by OpenGL using LWJGL.
Most of the people... if not all people who find world seeds such as the 'skull painting seed' 1282682090 and the original title screen seed 2151901553968352745 have used a special type of programming like a mini app that they use to find specific parts of the image, like a mountain, or a river. They then send all these seeds and a 'similar' image to a document for the actual player to look at. This is the reason they find these seeds.