What is the difference between the unary minus operator and the binary subtraction operator?
一元操作符负号和二元操作符减号的区别是什么？
Background subtraction and frame difference method are commonly used moving objects detection methods.
背景差法和帧间差法都是常用的运动目标检测方法。
The difference is found by subtraction.
用减法得出差额。
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