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      1 #include "opencv2/core/utility.hpp"
      2 #include "opencv2/imgproc.hpp"
      3 #include "opencv2/imgcodecs.hpp"
      4 #include "opencv2/highgui.hpp"
      5 
      6 #include <iostream>
      7 
      8 using namespace cv;
      9 using namespace std;
     10 
     11 int _brightness = 100;
     12 int _contrast = 100;
     13 
     14 Mat image;
     15 
     16 /* brightness/contrast callback function */
     17 static void updateBrightnessContrast( int /*arg*/, void* )
     18 {
     19     int histSize = 64;
     20     int brightness = _brightness - 100;
     21     int contrast = _contrast - 100;
     22 
     23     /*
     24      * The algorithm is by Werner D. Streidt
     25      * (http://visca.com/ffactory/archives/5-99/msg00021.html)
     26      */
     27     double a, b;
     28     if( contrast > 0 )
     29     {
     30         double delta = 127.*contrast/100;
     31         a = 255./(255. - delta*2);
     32         b = a*(brightness - delta);
     33     }
     34     else
     35     {
     36         double delta = -128.*contrast/100;
     37         a = (256.-delta*2)/255.;
     38         b = a*brightness + delta;
     39     }
     40 
     41     Mat dst, hist;
     42     image.convertTo(dst, CV_8U, a, b);
     43     imshow("image", dst);
     44 
     45     calcHist(&dst, 1, 0, Mat(), hist, 1, &histSize, 0);
     46     Mat histImage = Mat::ones(200, 320, CV_8U)*255;
     47 
     48     normalize(hist, hist, 0, histImage.rows, NORM_MINMAX, CV_32F);
     49 
     50     histImage = Scalar::all(255);
     51     int binW = cvRound((double)histImage.cols/histSize);
     52 
     53     for( int i = 0; i < histSize; i++ )
     54         rectangle( histImage, Point(i*binW, histImage.rows),
     55                    Point((i+1)*binW, histImage.rows - cvRound(hist.at<float>(i))),
     56                    Scalar::all(0), -1, 8, 0 );
     57     imshow("histogram", histImage);
     58 }
     59 static void help()
     60 {
     61     std::cout << "\nThis program demonstrates the use of calcHist() -- histogram creation.\n"
     62               << "Usage: \n" << "demhist [image_name -- Defaults to ../data/baboon.jpg]" << std::endl;
     63 }
     64 
     65 const char* keys =
     66 {
     67     "{@image|../data/baboon.jpg|input image file}"
     68 };
     69 
     70 int main( int argc, const char** argv )
     71 {
     72     help();
     73 
     74     CommandLineParser parser(argc, argv, keys);
     75     string inputImage = parser.get<string>(0);
     76 
     77     // Load the source image. HighGUI use.
     78     image = imread( inputImage, 0 );
     79     if(image.empty())
     80     {
     81         std::cerr << "Cannot read image file: " << inputImage << std::endl;
     82         return -1;
     83     }
     84 
     85     namedWindow("image", 0);
     86     namedWindow("histogram", 0);
     87 
     88     createTrackbar("brightness", "image", &_brightness, 200, updateBrightnessContrast);
     89     createTrackbar("contrast", "image", &_contrast, 200, updateBrightnessContrast);
     90 
     91     updateBrightnessContrast(0, 0);
     92     waitKey();
     93 
     94     return 0;
     95 }
     96