EDIT

Check for empty images before:

SELECT mrp.id, mrp.created, mrp.updated, mrp.uri, mr.id mrID, m.id, m.titleCache
FROM MediaRepresentationPart mrp INNER JOIN MediaRepresentation mr ON mr.id = mrp.representation_id
INNER JOIN Media m ON m.id = mr.media_id
WHERE mrp.uri IS NULL

New transformation rule may look like (with fixed width of 300, 600, 1700):

{"scheme":null,"host":{"replace":"mediahub.bo.berlin","search":"mediahub.bo.berlin"},"pathQueryFragment":{"replace":"api/File/$1/300.jpg","search":"api/File/Original/([\\-0-9a-f]+)/(.*)"},"mimeType":"image/jpeg","width":300,"height":300,"maxExtend":false}

or for crop

{"scheme":null,"host":{"replace":"pictures.bgbm.org","search":"mediahub.bo.berlin"},"pathQueryFragment":{"replace":"digilib/Scaler/?fn=mediacloud/org1/$1/original/&mo=crop&dw=200&dh=147&uvfix=1","search":"api/File/Original/([\\-0-9a-f]+)/(.*)"},"mimeType":"image/jpeg","width":200,"height":147,"maxExtend":false}

or for flexible width uncroped

{"scheme":null,"host":{"replace":"pictures.bgbm.org","search":"mediahub.bo.berlin"},"pathQueryFragment":{"replace":"digilib/Scaler/IIIF/mediacloud!org1!$1/full/!400,400/0/default.jpg","search":"api/File/Original/([\\-0-9a-f]+)/(.*)"},"mimeType":"image/jpeg","width":400,"height":400,"maxExtend":true}

DR:

...
Original: https://mediahub.bo.berlin/api/File/Original/1adb62d8-0b67-4128-927b-b713d164f98e/Sisymbrium_aegyptiacum_E1.JPG
Vorberechnet: https://mediahub.bo.berlin/api/File/1adb62d8-0b67-4128-927b-b713d164f98e/300.jpg
Vorberechnet: https://mediahub.bo.berlin/api/File/1adb62d8-0b67-4128-927b-b713d164f98e/600.jpg
Vorberechnet: https://mediahub.bo.berlin/api/File/1adb62d8-0b67-4128-927b-b713d164f98e/1700.jpg
Dynamisch über den IIIF Scaler:
https://pictures.bgbm.org/digilib/Scaler/IIIF/mediacloud!org1!1adb62d8-0b67-4128-927b-b713d164f98e/full/!400,400/0/default.jpg
Über Andreas K. medinfo Service:
https://image.bgbm.org/metadata/info?file=mediacloud/org1/1adb62d8-0b67-4128-927b-b713d164f98e/original
...