balance.cpp

#include <stdio.h>
#include <opencv2/opencv.hpp>

using namespace cv;
using namespace std; 

/// perform the Simplest Color Balancing algorithm
void SimplestCB(Mat& in, Mat& out, float percent) {
    assert(in.channels() == 3);
    assert(percent > 0 && percent < 100);

    float half_percent = percent / 200.0f;

    vector<Mat> tmpsplit; split(in,tmpsplit);
    for(int i=0;i<3;i++) {
        //find the low and high precentile values (based on the input percentile)
        Mat flat; tmpsplit[i].reshape(1,1).copyTo(flat);
        cv::sort(flat,flat,CV_SORT_EVERY_ROW + CV_SORT_ASCENDING);
        int lowval = flat.at<uchar>(cvFloor(((float)flat.cols) * half_percent));
        int highval = flat.at<uchar>(cvCeil(((float)flat.cols) * (1.0 - half_percent)));
        cout << lowval << " " << highval << endl;
        
        //saturate below the low percentile and above the high percentile
        tmpsplit[i].setTo(lowval,tmpsplit[i] < lowval);
        tmpsplit[i].setTo(highval,tmpsplit[i] > highval);
        
        //scale the channel
        normalize(tmpsplit[i],tmpsplit[i],0,255,NORM_MINMAX);
    }
    merge(tmpsplit,out);
}

// Input as first arg and output name as arg2
int main(int argc, char* argv[]) {
    Mat tmp,im = imread(argv[1]);
    SimplestCB(im,tmp,1);
    imwrite(argv[2] ,tmp);
    return 0;
}