OfxFlowTool getting ofFbo texture from OfImage

Hi there,

I’m trying to use OfxFlowTool. But not from the camera, but from OfImage. But
[ .h ]
ofFbo flowFbo;
ofImage image;
[ .cpp ] -> setup
flowFbo.allocate(CAM_WIDTH, CAM_HEIGHT);
[ .cpp ] -> update

image.draw(0, 0); // draw image to flowFbo

Doesn’t seems to capture the image. Do you know why?

P.S. I can see if I add
image.draw(0, 0) it draws 320 x 240 image.

System OSX
OpenFramework Version : v0.10.0