Thank you for writing back @meleu I think my "method" is somewhere inbetween. The fact is my non-merged full 0.37b5 romset (2241 roms) matches perfectly the 0.37b5 snaps (2241 snaps, a lot of work saved!) so what I do basically is:
1.- add
screenshot_directory = "/home/pi/RetroPie/roms/mame-mame4all/images/"
to
/opt/retropie/configs/mame-mame4all/retroarch.cfg
2.- move roms to Retropie/roms/mame-mame4all
2.- move snaps to Retropie/roms/mame-mame4all/images
3.- run
/opt/retropie/supplementary/scraper/scraper -add_not_found=true -append=true -download_images=false -image_dir="images" -image_path="images" -image_suffix="" -img_format="png" -img_workers=0 -no_thumb=true -thumb_only=false -thumb_suffix="" -use_ss=true -use_gdb=true -use_ovgdb=true -workers=4
Then gameslist.xml is created. I think those steps might be useful to users who already have a preference for snapshot packages.
However, I wonder what would be the best approach in the following scenario where there it no a rom <--> snap match:
1.- add
screenshot_directory = "/home/pi/RetroPie/roms/snes/images/"
to
/opt/retropie/configs/snes/retroarch.cfg
Move all 3438 No Intro SNES roms (Nintendo - Super Nintendo Entertainment System (20161130-222348_CM).dat) to
Retropie/roms/snes
Move all 3352 .png snapshots (No-Intro 20061119 Super Nintendo Entertainment System Screenshots.7z) to
Retropie/roms/snes/images
One more problem, snapshots name do not match rom names but it is relatively easy to sort it out.
Eg. Actraiser (U).png versus ActRaiser (USA).zip
So I have run a number or find and replace to swap U for USA, J for Japan and so on. Once .png files match their counterparts in the roms folder, the same scraper command is run to generate gamelist.xml
In any case, it is clear that there are less snapshots than rom files so there will be roms without snap. Any ideas on how to find out (list) what are those roms?
PS. I am going to have a good look at that link. Thank you for it.