linesToArrows.py

# Alternatively start with omero shell, instead of first 2 lines below, do this:
# $ bin/omero shell --login
#  conn = omero.gateway.BlitzGateway(client_obj=client)
conn = BlitzGateway("will", "ome", host="localhost", port=4064)
conn.connect()
updateService = conn.getUpdateService()
roiService = conn.getRoiService()
from omero.rtypes import rstring

imageId = 3731

result = roiService.findByImage(imageId, None)
for roi in result.rois:
    for s in roi.copyShapes():
        if isinstance(s, omero.model.LineI):
            s.markerStart = rstring("Arrow")  # OR 'None' to remove markerStart
            s.markerEnd = rstring("Arrow")
            updateService.saveObject(s)