samples/cpp/demhist.cpp

一个创建图像直方图的示例

#include "opencv2/core/utility.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
 
#include <iostream>
 
using namespace cv;
using namespace std;
 
int _brightness = 100;
int _contrast = 100;
 
Mat image;
 
/* 亮度/对比度回调函数 */
static void updateBrightnessContrast( int /*arg*/, void* )
{
    int histSize = 64;
    int brightness = _brightness - 100;
    int contrast = _contrast - 100;
 
    /*
* 算法来自 Werner D. Streidt
* (http://visca.com/ffactory/archives/5-99/msg00021.html)
     */
    double a, b;
    if( contrast > 0 )
    {
        double delta = 127.*contrast/100;
a = 255./(255. - delta*2);
b = a*(brightness - delta);
    }
    else
    {
        double delta = -128.*contrast/100;
a = (256.-delta*2)/255.;
b = a*brightness + delta;
    }
 
    Mat dst, hist;
image.convertTo(dst, CV_8U, a, b);
imshow("image", dst);
 
calcHist(&dst, 1, 0, Mat(), hist, 1, &histSize, 0);
    Mat histImage = Mat::ones(200, 320, CV_8U)*255;
 
normalize(hist, hist, 0, histImage.rows, NORM_MINMAX, CV_32F);
 
histImage = Scalar::all(255);
    int binW = cvRound((double)histImage.cols/histSize);
 
    for( int i = 0; i < histSize; i++ )
rectangle( histImage, Point(i*binW, histImage.rows),
                   Point((i+1)*binW, histImage.rows - cvRound(hist.at<float>(i))),
Scalar::all(0), -1, 8, 0 );
imshow("histogram", histImage);
}
 
const char* keys =
{
    "{help h||}{@image|baboon.jpg|输入图像文件}"
};
 
int main( int argc, const char** argv )
{
    CommandLineParser parser(argc, argv, keys);
parser.about("\n本程序演示了 calcHist() 的使用方法 - 直方图创建。\n");
    if (parser.has("help"))
    {
parser.printMessage();
        return 0;
    }
    string inputImage = parser.get<string>(0);
 
    // 加载源图像。 HighGUI 使用。
image = imread(samples::findFile(inputImage), IMREAD_GRAYSCALE);
    if(image.empty())
    {
std::cerr << "无法读取图像文件: " << inputImage << std::endl;
        return -1;
    }
 
    namedWindow("image", 0);
    namedWindow("histogram", 0);
 
    createTrackbar("brightness", "image", &_brightness, 200, updateBrightnessContrast);
    createTrackbar("contrast", "image", &_contrast, 200, updateBrightnessContrast);
 
updateBrightnessContrast(0, 0);
    waitKey();
 
    return 0;
}