Function to_one_bit 

pub fn to_one_bit(
    frame: &GlyphBuffer,
    map: &PatternMap,
    font: &Font<'_>,
    images: &impl Images,
) -> OneBitFrame

Draws frame as a one-bit target shows it: its colours in their roles’ patterns by map, glyphs from font, sprites’ one-bit pictures from images (render_with). The frame is drawn from the display’s top-left corner, and what lies past 400 × 240 pixels is cut off.