countNonZero

Usage

Counts the number of non-zero pixels in a matrix or image to quickly obtain the occurrences of a specific feature.

Interface

int countNonZero(InputArray src);

Parameters

Parameter	Description	Value Range	Input/Output
src	Input image.	Not null, single channel	Input

Return Values

Success: KP_CV_SUCCESS
Failure: an error code

Error Codes

Error Code	Description
INVALID_PARAM_MSG	The input image is null.
NOT_SUPPORT_MSG	The type of the input image is not supported.

Example

#include <opencv2/opencv.hpp>
#include <iostream>

int main() {
    // Create a 5x5 binary image.
    cv::Mat src = (cv::Mat_<uint8_t>(5, 5) << 0, 0, 0, 0, 0,
                                              0, 1, 1, 1, 0,
                                              0, 1, 0, 1, 0,
                                              0, 1, 1, 1, 0,
                                              0, 0, 0, 0, 0);

    // Count the number of non-zero pixels.
    int count = cv::countNonZero(src);

    std::cout << "Number_of_non-zero_pixels: " << count << std::endl;

    return 0;
}

Output:

Number of non-zero pixels: 8

Parent topic: Interface Definition