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minimum value per pixel (w.r.t channel) in a 3 channel image

asked 2016-05-30 06:36:23 -0600

hyder gravatar image

Hi everyone,

Is there any function in openCV which can return the minimum/maximum value of a pixel w.r.t channel in a 3 channel image (e.g. a BGR image) like the following available in MATLAB:

temp = min(im, [], 3);

I know that you can use nested loops to access each pixel using Mat::at<type>(i,j) operator and then use min function twice to get the minimum value per pixel like this:

for (int m = 0; m<src.rows; m++)
        for (int n = 0; n<src.cols; n++)
            intensity =<Vec3b>(m, n);
  <uchar>(m, n) = min(min(intensity.val[0], intensity.val[1]), intensity.val[2]);

but this seems slower and I am looking for a more efficient way to do this.


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answered 2016-06-02 01:10:44 -0600

hyder gravatar image

I found another way of doing this:

Mat temp, minChannel, bgr[3];

split(src, bgr);                           //split src into B,G,R channels
(cv::min)(bgr[0], bgr[1], temp);           //find minimum between B and G channels
(cv::min)(temp, bgr[2], minChannel);       //find minimum between temp and R channels
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answered 2016-05-30 07:29:07 -0600

LBerger gravatar image

updated 2016-05-31 02:22:26 -0600

You can try like this :

 vector<Mat> x;
 vector<double> minChannel;
 vector<double> maxChannel;
 for (int i=0;i<x.size();i++)

resuts are in vectors minChannels and maxChannels

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Thanks for the reply. Shouldn't it be split(src, x) rather than split(x, src)?

hyder gravatar imagehyder ( 2016-05-31 01:54:02 -0600 )edit

Oops..Yes thanks

LBerger gravatar imageLBerger ( 2016-05-31 02:22:53 -0600 )edit

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Asked: 2016-05-30 06:36:23 -0600

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Last updated: Jun 02 '16