CODEWITHSUNDEEP
opencvimage-processinghistogram
ashwin shanker
ashwin shanker

Reputation: 313

Histogram of an array of values in OpenCv

I have a matrix of 630 values (values range from 0-35)...

I want to find the most frequently occurring value in this matrix. So how do I write a histogram for this? Also is there any other way that I can find the most frequently occurring value (I don't want to use counters as i will need 36 counters and My code would become very inefficient)

..Thanks!

Upvotes: 1

Views: 4135

Answers (2)

Zaphod
Zaphod

Reputation: 1927

You can use calcHist with a Mat of size 1xN, where N is 630 in your case.

I don't understand your argument against counters. To build the histogram, you must use counters anyway. There are ways to make counting very efficient.

OR

Assuming your image is a cv::Mat variable im with size 1x630 and type CV_8UC1, try:

std::vector<int> counts(36, 0);
for (int c = 0; c < 630; c++)
    counts.at(im.at<unsigned char>(1, c)) += 1;
std::cout << "Most frequently occuring value: " << std::max_element(counts);

This uses counting, but will not take more than 0.1ms on an average PC.

Upvotes: 3

LovaBill
LovaBill

Reputation: 5139

Why not do it manually?

Mat myimage(cvSize(1,638), CV_8U);
randn(myimage, Scalar::all(128), Scalar::all(20)); //Random fill
vector<int> histogram(256);
for (int i=0;i<638;i++)
    histogram[(int)myimage.at<uchar>(i,0)]++;

Upvotes: 1

Related Questions