Help me!! Flower Detection

I want to draw graphs. From flowers. By then I will start from the point of 0 degrees for most of the distance. Then draw a graph to bring up a chart like the unfolding petals.

I want to know the number of petals.

Help me.

ex.image>>> http://pic.free.in.th/id/3393c208f59da097297abc76d3e86945

Sorry, my English is not good.