Man pages matching name visir_util_undistort in section 7:

visir_util_undistort.7.en	debian 10 / cpl-plugin-visir-doc
visir_util_undistort.7.en	debian 11 / cpl-plugin-visir-doc
visir_util_undistort.7.en	debian 12 / cpl-plugin-visir-doc