Function ReadByteMask 

pub unsafe extern "C" fn ReadByteMask(
    mag: *mut *mut f32,
    infiles: *mut infileT,
    linelen: c_long,
    nlines: c_long,
    tileparams: *mut tileparamT,
    params: *mut paramT,
) -> c_int

Read signed byte mask value; set magnitude to zero where byte mask is zero or where pixel is close enough to edge as defined by edgemask parameters; leave magnitude unchanged otherwise.