Constant turbojpeg_sys::TJPF_TJPF_GRAY

pub const TJPF_TJPF_GRAY: TJPF = 6;

Grayscale pixel format. Each 1-sample pixel represents a luminance (brightness) level from 0 to the maximum sample value (255 for 8-bit samples, 4095 for 12-bit samples, and 65535 for 16-bit samples.)