OpenCV C++開發 第二節：圖像處理（十、直方圖均衡化、直方圖反向投影）

一、直方圖均衡化

代碼：

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>

using namespace cv;
int main(int argc, char** argv) {
	Mat src, dst;
	src = imread("C:\\Users\\Administrator\\Desktop\\timg.jpg");
	if (!src.data) {
		printf("could not load image...\n");
		return -1;
	}

	cvtColor(src, src, CV_BGR2GRAY);
	equalizeHist(src, dst);
	char INPUT_T[] = "input image";
	char OUTPUT_T[] = "result image";
	namedWindow(INPUT_T, CV_WINDOW_AUTOSIZE);
	namedWindow(OUTPUT_T, CV_WINDOW_AUTOSIZE);

	imshow(INPUT_T, src);
	imshow(OUTPUT_T, dst);

	waitKey(0);
	return 0;
}
           

以上代碼中主要的幾個知識點解釋下：

1.equalizeHist(src, dst);

這個就是直方圖均衡化提高圖像對比度。src是源圖像，dst是目的圖像。

二、直方圖反向投影

代碼：

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>

using namespace std;
using namespace cv;

Mat src; Mat hsv; Mat hue;
int bins = 12;
void Hist_And_Backprojection(int, void*);
int main(int argc, char** argv) {
	src = imread("C:\\Users\\Administrator\\Desktop\\test.png");
	if (src.empty()) {
		printf("could not load image...\n");
		return -1;
	}
	const char*  window_image = "input image";
	namedWindow(window_image, CV_WINDOW_NORMAL);
	namedWindow("BackProj", CV_WINDOW_NORMAL);
	namedWindow("Histogram", CV_WINDOW_NORMAL);

	cvtColor(src, hsv, CV_BGR2HSV);
	hue.create(hsv.size(), hsv.depth());
	int nchannels[] = { 0, 0 };
	mixChannels(&hsv, 1, &hue, 1, nchannels, 1);

	createTrackbar("Histogram Bins:", window_image, &bins, 180, Hist_And_Backprojection);
	Hist_And_Backprojection(0, 0);

	imshow(window_image, src);
	waitKey(0);
	return 0;
}

void Hist_And_Backprojection(int, void*) {
	float range[] = { 0, 180 };
	const float *histRanges = { range };
	Mat h_hist;
	calcHist(&hue, 1, 0, Mat(), h_hist, 1, &bins, &histRanges, true, false);
	normalize(h_hist, h_hist, 0, 255, NORM_MINMAX, -1, Mat());

	Mat backPrjImage;
	calcBackProject(&hue, 1, 0, h_hist, backPrjImage, &histRanges, 1, true);
	imshow("BackProj", backPrjImage);

	int hist_h = 400;
	int hist_w = 400;
	Mat histImage(hist_w, hist_h, CV_8UC3, Scalar(0, 0, 0));
	int bin_w = (hist_w / bins);
	for (int i = 1; i < bins; i++) {
		rectangle(histImage,
			Point((i - 1)*bin_w, (hist_h - cvRound(h_hist.at<float>(i - 1) * (400 / 255)))),
			//Point(i*bin_w, (hist_h - cvRound(h_hist.at<float>(i) * (400 / 255)))),
			Point(i*bin_w, hist_h),
			Scalar(0, 0, 255), -1);
	}
	imshow("Histogram", histImage);

	return;
}
           

以上代碼中主要的幾個知識點解釋下：

1.calcBackProject(&hue, 1, 0, h_hist, backPrjImage, &histRanges, 1, true);

計算方向投影的，暫時不知道有啥卵用，有用了再更新進來吧。