Filter2D Meaning

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hy, can anyone give me the explaination of these 2 lines of code.

c1 = cv2.filter2D(img2, -1, h/n1, borderType=cv2.BORDER_REFLECT) c2 = cv2.filter2D(img, -1, h, borderType=cv2.BORDER_REFLECT)2 / (n*n1)

i am not able to get the meaning of img2 and cv2.filter2D(img, -1, h, borderType=cv2.BORDER_REFLECT)2 / (n*n1).

what it exectly does. i want to write the same thing in java. appreciated if someone can help me out help me !!