Function fz_open_image_decomp_stream_from_buffer 

pub unsafe extern "C" fn fz_open_image_decomp_stream_from_buffer(
    ctx: *mut fz_context,
    arg1: *mut fz_compressed_buffer,
    l2factor: *mut c_int,
) -> *mut fz_stream

Open a stream to read the decompressed version of a buffer,
with optional log2 subsampling.

l2factor = NULL for no subsampling, or a pointer to an integer
containing the maximum log2 subsample factor acceptable (0 =
none, 1 = halve dimensions, 2 = quarter dimensions etc). If
non-NULL, then *l2factor will be updated on exit with the actual
log2 subsample factor achieved.