Function stb::dxt::stb_compress_dxt_block

pub fn stb_compress_dxt_block(
    dest: &mut [u8], 
    src_rgba_four_bytes_per_pixel: &[u8], 
    alpha: i32, 
    mode: CompressionMode
)

Call stb_compress_dxt_block() for every block (you must pad) source should be a 4x4 block of RGBA data in row-major order; Alpha channel is not stored if you specify alpha=0 (but you must supply some constant alpha in the alpha channel). You can turn on dithering and "high quality" using mode.