Remove the background / cropping the region of interest

Hello,

 I'm doing a project to estimate the freshness of egg. I want to crop the egg image for further analysis or remove the black background. Though the background is black, when I take the G component for further analysis, intensity value  of black background varies from 0 to 20( due to some leakage of light or some illumination problem as the expt is done using a black box). This variation is undesirable while taking the image for further processing.
I want to either crop the egg image( oval shape) or I want to set the black bg in G component to zero ie, no variation from 0. It's really urgent. Please help me in this regard.

Answer 1

[Image Analyst]

See attached code that will produce this figure:

[Anagha]

Thank you. Your code works perfectly. :)