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This question was answered by Rotem on stackoverflow, view it here

I needed to invert my image to black background white foreground so that area could count the white pixels.

_, src_thresh = cv.threshold(src_gray, 0, 255, cv.THRESH_BINARY_INV + cv.THRESH_OTSU)
contours, _ = cv.findContours(src_thresh, cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE)