int im_remosaic( IMAGE *in, IMAGE *out,
const char *old_str, const char *new_str )
Unlike im_global_balance(3) images are substituted based on their filenames. The rightmost occurence of the string old_str is swapped for new_str, that file is opened, and that image substituted for the old image.
It's convenient for multispectral images. You can mosaic one band, then use that mosaic as a template for mosaicing the others automatically.