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# minimum value per pixel (w.r.t channel) in a 3 channel 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 = src.at<Vec3b>(m, n);
rgbmin.at<uchar>(m, n) = min(min(intensity.val, intensity.val), intensity.val);
}
}


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

Thanks

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## 2 answers

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I found another way of doing this:

Mat temp, minChannel, bgr;

split(src, bgr);                           //split src into B,G,R channels
(cv::min)(bgr, bgr, temp);           //find minimum between B and G channels
(cv::min)(temp, bgr, minChannel);       //find minimum between temp and R channels

more

You can try like this :

 vector<Mat> x;
split(src,x)
vector<double> minChannel;
vector<double> maxChannel;
minChannel.resize(x.size());
maxChannel.resize(x.size());
for (int i=0;i<x.size();i++)
minMaxLoc(x[i],&minChannel[i],&maxChannel[i]);


resuts are in vectors minChannels and maxChannels

more

## Comments

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

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Asked: 2016-05-30 06:36:23 -0500

Seen: 1,408 times

Last updated: Jun 02 '16