java -jar mkgmap.jar --gmapsupp otm-hungary.img otm-slovenia.img
I tried that but the resulting file is only 2.5KB small: ░ tamasgal@silentbox:~/opt/mkgmap-r4909 ░ 17:35:23 > java -jar mkgmap.jar --gmapsupp otm-hungary.img otm-slovenia.img Mkgmap version 4909 Time started: Thu Jul 13 17:35:36 CEST 2023 Number of MapFailedExceptions: 0 Number of ExitExceptions: 0 Time finished: Thu Jul 13 17:35:36 CEST 2023 Total time taken: 267 ms ░ tamasgal@silentbox:~/opt/mkgmap-r4909 ░ 17:35:36 > ls -alh total 1563104 drwxrwxr-x@ 15 tamasgal staff 480B Jul 13 17:35 . drwxr-xr-x 9 tamasgal staff 288B Jul 13 16:17 .. -rw-rw-r--@ 1 tamasgal staff 18K Jun 5 10:29 LICENCE -rw-rw-r--@ 1 tamasgal staff 2.7K Jun 5 10:29 README drwxrwxr-x@ 10 tamasgal staff 320B Jun 5 10:31 doc drwxrwxr-x@ 10 tamasgal staff 320B Jun 5 10:29 examples -rw-r--r-- 1 tamasgal staff 2.5K Jul 13 17:35 gmapsupp.img drwxrwxr-x@ 5 tamasgal staff 160B Jun 5 10:29 lib -rw-rw-r--@ 1 tamasgal staff 2.3M Jun 5 10:29 mkgmap.jar -rw-r--r-- 1 tamasgal staff 5.0K Jul 13 17:35 osmmap.img -rw-r--r-- 1 tamasgal staff 155B Jul 13 17:35 osmmap.tdb -rw-r--r--@ 1 tamasgal staff 126M Jul 13 16:24 otm-germany-contours.img -rw-r--r--@ 1 tamasgal staff 43M Jul 13 16:28 otm-hungary-contours.img -rw-r--r--@ 1 tamasgal staff 346M Jul 13 16:28 otm-hungary.img -rw-r--r--@ 1 tamasgal staff 246M Jul 13 16:29 otm-slovenia.img