First input image, 1- or 3-channel, 8-bit or 32-bit floating point.
Second input image of the same type and the same size as src1 .
Accumulator image with the same number of channels as input images, 32-bit or 64-bit floating-point.
Optionalmask: Mat
Optional operation mask.
Adds the per-element product of two input images to the accumulator image.
https://docs.opencv.org/4.x/d7/df3/group__imgproc__motion.html#ga82518a940ecfda49460f66117ac82520