how to find spot pixels in image?

Hello image analyst, my work is to grade mango images. I've found the centroid, majoraxislength for the image.. now i need to find the number of spot pixels, so that i ll get ratio of spot pixels. As my image is having black background, I find difficult to process further. how can I exclude background pixels from processing? Plz help me. the image is posted for ur reference.

[swathi]

Some1 plz help me in this...

[swathi]

I am explaining the problem statement more clearly, hoping some one would really help me out. the project is to classify the mangoes as grade 1, grade 2 etc based on size, color and spots features. I am in the 3rd stage to obtain spot pixel information, so i can classify them as grad 1-3 or rejected. if the number of pixels are more, the fruit will be rejected. my problem is in finding the spot pixel information. my work has been stopped as I've not received any solution. looking forward for your help.

[swathi]

hello, can I use bchannel of lab color model to find and count spot pixels? in that case, how can i not include background pixels as even they are black in color? looking forward for some assistance.