How does picture memory work?

Question

Graphic arts

So I asked myself a question. How does memory work for a drawing (graphic)?
I know that one color consists of 8 characters (that is, bytes). But here's the question. If I make the format, for example, 1280 by 1024, will I get a size of 1310720 bytes (1.25 MB)? Or does it work somehow differently? Or different colors weigh their number of bytes?
And about the same characters. One letter is a byte (or bit) If I write 1024 characters, will the file weigh 1 KB? I turned down this question, but I still hope I'm right

Answer 1

Each color has its own number. Different colors have different number lengths) Naturally, the more pixels with colors that have shorter numbers, and the fewer pixels that have longer numbers, the less the picture weighs))