Whoever even vaguely worked with image files knows very well that BMP is a lossless but also near-to-zero compression format that results in very high file size; for example as reference I just tried to convert a 1920x1080 screenshot of Tera to BMP(@24 bit) and the file size went up to almost 6 MB.
If you ask for an image 1920x1080(not UP TO 1920x1080, you literally ask for a 1920x1080 one) in either BMP or PSD formant AND under 3 MB sorry but you have no idea what you're talking about. No way and I mean NO WAY you can make a 1920x1080 BMP under 3 MB unless it's a white screen or something extremely low detailed.
