Python Bitwise OR

Question

I have the following C++ code:

// Load image from vector
        cv::Mat image = imread(filenames[i]);

        //  option = black 
        if (arg == "black" | arg == "all") 
            {

            // Extracting colors - BGR (black backround)
            // Blue
            inRange(image, Scalar(190, 0, 0), Scalar(255, 50, 50), blue);
            // Green
            inRange(image, Scalar(0, 190, 0), Scalar(50, 255, 50), green);
            // Red
            inRange(image, Scalar(0, 0, 190), Scalar(50, 50, 255), red);
            // White
            inRange(image, Scalar(235, 235, 235), Scalar(255, 255, 255), white);
            // Silver
            inRange(image, Scalar(180, 180, 190), Scalar(200, 200, 220), silver);           

            // bitwise OR mask
            mask = blue|green|red|white|silver;

            }

        //  option = wooden 
        else
            {

            // Extracting colors - BGR (wooden backround)
            // Blue
            inRange(image, Scalar(190, 0, 0), Scalar(255, 50, 50), blue);
            // Green
            inRange(image, Scalar(0, 190, 0), Scalar(50, 255, 50), green);
            // Red
            inRange(image, Scalar(0, 0, 190), Scalar(50, 50, 255), red);
            // White
            inRange(image, Scalar(235, 235, 235), Scalar(255, 255, 255), white);
            // Silver
            inRange(image, Scalar(190, 190, 200), Scalar(220, 220, 230), silver);
            // Black
            inRange(image, Scalar(0, 0, 0), Scalar(40, 40, 40), black);


            // bitwise OR mask
            mask = blue|green|red|white|silver|black;


            }



        // Store mask points into a vector
        vector<Point> pts;
        findNonZero(mask, pts);

which I want to translate to Python. I am done with almost every part but not the bitwise OR mask part.

I tried the following:

mask = np.logical_or.reduce((mask == blue, mask == green, mask == red, mask == white, mask == silver))

however it did not work for me.

What's the Python equivalent of this operation?

As an aside if (arg == "black" | arg == "all") - you want ||, not |. — user2100815
– user2100815, Commented Aug 27, 2018 at 13:22
there is no logical or used in your c++ code, there is only bitwise or. So to do the same in python, you should use bitwise or there as well (which is |, just like in C++), not logical. — Zinki
– Zinki, Commented Aug 27, 2018 at 13:22
@Zinki thank you for your clarification, I corrected it in my post. So the syntax remains the same in Python as well? — Schütze
– Schütze, Commented Aug 27, 2018 at 13:24

Zinki · Accepted Answer · 2018-08-27 13:32:38Z

2

there is no logical or used in your c++ code, there is only bitwise or. So to do the same in python, you should use bitwise or there as well (which is |, just like in C++), not logical.

So

        mask = blue|green|red|white|silver|black;

in C++ should be equivalent to

        mask = blue|green|red|white|silver|black

in python.

answered Aug 27, 2018 at 13:32

Zinki

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