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Opencv sum()[]

asked 2013-06-04 22:14:02 -0500

xiaojidan gravatar image

I am new to opencv , I do not understand the function "sum".

Mat img=(Mat_<double>(3,3)<<0,-1,0,-1,5,-1,2,-1,0); double rr=sum(img)[0]; cout<<"rr"<<rr&lt;<endl;< p="">

waitKey(0);
return 0;

What is the meaning of this function "sum", sum(img)[0] is standing for?? sum(img)[1] is standing for ? sum(img)[2] is stranding for??

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answered 2013-06-05 02:41:19 -0500

berak gravatar image

sum() returns a Scalar with the sum of all pixels per channel

so, for a 3channel img (think a color image),

Scalar s = sum(img);
// s[0] is the sum of the 1st channel (B probably)
// s[1] is the sum of the 2nd channel (G probably)
// s[2] ...

in your case, the Mat only has one channel, so double s = sum(mat)[0] is the way to access it.

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Thank you

xiaojidan gravatar imagexiaojidan ( 2013-06-05 06:29:20 -0500 )edit
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Asked: 2013-06-04 22:14:02 -0500

Seen: 1,438 times

Last updated: Jun 05 '13