Common pre processing in blob extracting

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Hi! I'm trying to do some blob extracting and the normal procedure I've seen in a lot of example codes is:

• after some background butraction/modeling/etc we have cv::Mat I (black and white)
• apply some processing like blur, erode, dilate
• apply findContours
• filter blob (like with contourArea)

I'd like to know if there are some common way of handling the pre-processing before find contours or if they can be avoided because of computationally too expencive