Repository: opencv
Issue: Maybe an overflow bug in cascadedetect.cpp
Labels: question (invalid tracker),category: objdetect

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##### System information (version)
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- OpenCV => 4.2
- Operating System / Platform => Windows 64 Bit
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- OpenCV => 4.2
- Operating System / Platform => Windows 64 Bit
- Compiler => Visual Studio 2017

##### Detailed description

At [this line](https://github.com/opencv/opencv/blob/master/modules/objdetect/src/cascadedetect.cpp#L648) of cascadedetect.cpp, the `computeChannels` method of `HaarEvaluator` computes integral image of input image and its squared pixel values with `depth=CV_32S` for both `sum` and `sqsum`. Also at [this line](https://github.com/opencv/opencv/blob/master/modules/objdetect/src/cascadedetect.cpp#L525), `sbuf` (which I belive is the buffer of the integral images) has type of `CV_32S`. 

Even a 512x512 lena.jpg has `sqsum` exceed 32bits integer range, `sum` would soon be overflow for larger image. So I suspect that it would cause overflow bug thus make the whole code wrong except that the code was misunderstood (in this case, I apologize for my mistake).

##### Steps to reproduce

```.cpp
cascade.detectMultiScale()
```

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