Screenshot capturing

[J7N]

I can't speak of how and when BS.Player does picture reampling.

But the effect of color change you see is called mismatch in video level. Videos normally decode to brightness range [16,235] and upon playback must be corrected to full range [0,255] in order to get true black and white as intended. I have no idea why it's as stupid, probably some legacy from broadcast TV standards.

Unlike resize, this correction is difficult to do in a graphics editor (not all have histogram display) and you probably have to use ffdshow to capture in the first place.