Hello
Please try below code
procedure TMainForm.UniButton18Click(Sender: TObject);
begin
with UniMap1, JSInterface do
begin
JSAssign('uniMap.options.crs', [JSStatement('L.CRS.Simple')]);
JSCall('uniMap.setMaxBounds', [JSStatement('new L.LatLngBounds([0,500], [500,0])')]);
UniSession.AddJS('var imageUrl = "http://www.lib.utexas.edu/maps/historical/newark_nj_1922.jpg";');
UniSession.AddJS('var imageBounds = [[250,0], [0,250]];');
UniSession.AddJS('L.imageOverlay(imageUrl, imageBounds).addTo('+JSName+'.uniMap);');
end;
end;