checkState((createdNow && (creationTime == 0)) || (!createdNow && (creationTime > 0)), "exactly one of created now or creation time must be set");
checkState((width > 0) && (height > 0), "width and height must be set");
}
checkState((createdNow && (creationTime == 0)) || (!createdNow && (creationTime > 0)), "exactly one of created now or creation time must be set");
checkState((width > 0) && (height > 0), "width and height must be set");
}