Leica seems to embed multiple Jpegs in the DNG including what appears to be the same full size jpeg you could have as a separate file. exiftool can extract them. This tool chooses the large one. Not sure if selecting them would be a useful option, 2 of them share the same name which is also weird.
brian@Brians-M5MaxBook 100LEICA % exiftool -b -IFD0:PreviewImage L1000672.DNG > L1000672_thumb.jpg
brian@Brians-M5MaxBook 100LEICA % exiftool -b -SubIFD1:PreviewImage L1000672.DNG > L1000672_preview.jpg
brian@Brians-M5MaxBook 100LEICA % exiftool -b -SubIFD2:JpgFromRaw L1000672.DNG > L1000672_full.jpg
brian@Brians-M5MaxBook 100LEICA % ls -ltr
total 1611264
-rwx------ 1 brian staff 93011968 Mar 28 09:17 L1000672.DNG
-rwx------ 1 brian staff 122461 Mar 28 12:00 L1000672_thumb.jpg
-rwx------ 1 brian staff 653174 Mar 28 12:01 L1000672_preview.jpg
-rwx------ 1 brian staff 15405995 Mar 28 12:01 L1000672_full.jpg
submitting this for informational puproses.
Interesting Leica DNGs
Leica seems to embed multiple Jpegs in the DNG including what appears to be the same full size jpeg you could have as a separate file. exiftool can extract them. This tool chooses the large one. Not sure if selecting them would be a useful option, 2 of them share the same name which is also weird.
brian@Brians-M5MaxBook 100LEICA % exiftool -b -IFD0:PreviewImage L1000672.DNG > L1000672_thumb.jpg
brian@Brians-M5MaxBook 100LEICA % exiftool -b -SubIFD1:PreviewImage L1000672.DNG > L1000672_preview.jpg
brian@Brians-M5MaxBook 100LEICA % exiftool -b -SubIFD2:JpgFromRaw L1000672.DNG > L1000672_full.jpg
brian@Brians-M5MaxBook 100LEICA % ls -ltr
total 1611264
-rwx------ 1 brian staff 93011968 Mar 28 09:17 L1000672.DNG
-rwx------ 1 brian staff 122461 Mar 28 12:00 L1000672_thumb.jpg
-rwx------ 1 brian staff 653174 Mar 28 12:01 L1000672_preview.jpg
-rwx------ 1 brian staff 15405995 Mar 28 12:01 L1000672_full.jpg
submitting this for informational puproses.