hist calc – opencv

referenced from opencv

#include “opencv2/highgui/highgui.hpp”

#include “opencv2/imgproc/imgproc.hpp”

#include <iostream>

#include <stdio.h>

using namespace std;

using namespace cv;

 

/** * @function main

*/

int main( int argc, char** argv )

{

Mat src, dst;

 

/// Load image

src = imread( argv[1], 1 );

 

if( !src.data )

{ return -1; }

 

/// Separate the image in 3places ( B, G and R )

vector<Mat> bgr_planes;

split( src, bgr_planes );

 

/// Establish the number of bins

int histSize = 256;

 

/// Set the ranges ( for B,G,R) )

float range[] = { 0, 256 };

const float* histRange = { range };

 

bool uniform = true;bool accumulate = false;

Mat b_hist, g_hist, r_hist;

 

/// Compute the histograms:

calcHist( &bgr_planes[0], 1, 0, Mat(), b_hist, 1, &histSize, &histRange, uniform, accumulate );

calcHist( &bgr_planes[1], 1, 0, Mat(), g_hist, 1, &histSize, &histRange, uniform, accumulate );

calcHist( &bgr_planes[2], 1, 0, Mat(), r_hist, 1, &histSize, &histRange, uniform, accumulate );

 

 

// Draw the histograms for B, G and R

int hist_w = 512; int hist_h = 400;

int bin_w = cvRound( (double) hist_w/histSize );

 

Mat histImage( hist_h, hist_w, CV_8UC3, Scalar( 0,0,0));

 

/// Normalize the result to [ 0, histImage.rows ]

normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );

normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );

normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );

 

 

/// Draw for each channel

for( int i = 1; i < histSize; i++ )

{

line( histImage,Point( bin_w*(i-1), hist_h – cvRound(b_hist.at<float>(i-1)) ) ,

Point( bin_w*(i), hist_h – cvRound(b_hist.at<float>(i)) ),

Scalar( 255, 0, 0), 2, 8, 0 );

line( histImage,Point( bin_w*(i-1), hist_h – cvRound(g_hist.at<float>(i-1)) ) ,

Point( bin_w*(i), hist_h – cvRound(g_hist.at<float>(i)) ),

Scalar( 255, 0, 0), 2, 8, 0 );

line( histImage,Point( bin_w*(i-1), hist_h – cvRound(r_hist.at<float>(i-1)) ) ,

Point( bin_w*(i), hist_h – cvRound(r_hist.at<float>(i)) ),

Scalar( 255, 0, 0), 2, 8, 0 );

}

 

/// Display

namedWindow(“calcHist Demo”, CV_WINDOW_AUTOSIZE );

imshow(“calcHist Demo”, histImage );

waitKey(0);

return 0;

}