1/**
2 * @function calcHist_Demo.cpp
3 * @brief Demo code to use the function calcHist
4 * @author
5 */
6
7#include "opencv2/highgui/highgui.hpp"
8#include "opencv2/imgcodecs.hpp"
9#include "opencv2/imgproc/imgproc.hpp"
10#include <iostream>
11#include <stdio.h>
12
13using namespace std;
14using namespace cv;
15
16/**
17 * @function main
18 */
19int main( int, char** argv )
20{
21  Mat src, dst;
22
23  /// Load image
24  src = imread( argv[1], 1 );
25
26  if( src.empty() )
27    { return -1; }
28
29  /// Separate the image in 3 places ( B, G and R )
30  vector<Mat> bgr_planes;
31  split( src, bgr_planes );
32
33  /// Establish the number of bins
34  int histSize = 256;
35
36  /// Set the ranges ( for B,G,R) )
37  float range[] = { 0, 256 } ;
38  const float* histRange = { range };
39
40  bool uniform = true; bool accumulate = false;
41
42  Mat b_hist, g_hist, r_hist;
43
44  /// Compute the histograms:
45  calcHist( &bgr_planes[0], 1, 0, Mat(), b_hist, 1, &histSize, &histRange, uniform, accumulate );
46  calcHist( &bgr_planes[1], 1, 0, Mat(), g_hist, 1, &histSize, &histRange, uniform, accumulate );
47  calcHist( &bgr_planes[2], 1, 0, Mat(), r_hist, 1, &histSize, &histRange, uniform, accumulate );
48
49  // Draw the histograms for B, G and R
50  int hist_w = 512; int hist_h = 400;
51  int bin_w = cvRound( (double) hist_w/histSize );
52
53  Mat histImage( hist_h, hist_w, CV_8UC3, Scalar( 0,0,0) );
54
55  /// Normalize the result to [ 0, histImage.rows ]
56  normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
57  normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
58  normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
59
60  /// Draw for each channel
61  for( int i = 1; i < histSize; i++ )
62  {
63      line( histImage, Point( bin_w*(i-1), hist_h - cvRound(b_hist.at<float>(i-1)) ) ,
64                       Point( bin_w*(i), hist_h - cvRound(b_hist.at<float>(i)) ),
65                       Scalar( 255, 0, 0), 2, 8, 0  );
66      line( histImage, Point( bin_w*(i-1), hist_h - cvRound(g_hist.at<float>(i-1)) ) ,
67                       Point( bin_w*(i), hist_h - cvRound(g_hist.at<float>(i)) ),
68                       Scalar( 0, 255, 0), 2, 8, 0  );
69      line( histImage, Point( bin_w*(i-1), hist_h - cvRound(r_hist.at<float>(i-1)) ) ,
70                       Point( bin_w*(i), hist_h - cvRound(r_hist.at<float>(i)) ),
71                       Scalar( 0, 0, 255), 2, 8, 0  );
72  }
73
74  /// Display
75  namedWindow("calcHist Demo", WINDOW_AUTOSIZE );
76  imshow("calcHist Demo", histImage );
77
78  waitKey(0);
79
80  return 0;
81
82}
83