本節知識點

1,讀寫影象

a,imread可以載入灰度圖或者RGB影象

b,imwrite儲存影象，型別由副檔名決定

2,讀寫影象的畫素

a,讀取灰度影象畫素點的值(CV_8UC1)

Scalar intensity=img.at<uchar>(y,x);

或者

Scalar intensity=img.at<uchar>(Point(x,y))

3,讀一個RGB畫素點的畫素值

Vec3f intensity=img.at<Vec3f>(y,x)

float blue=intensity.val[0]

float green=intensity.val[1]

float red=intensity.val[2]

4,修改畫素值

a,修改灰度影象畫素值

img.at<uchar>(y,x)=128

b,修改RGB三通道影象畫素值

img.at<Vec3b>(y,x)[0]=128;//blue 通道

img.at<Vec3b>(y,x)[1]=128;//green 通道

img.at<Vec3b>(y,x)[2]=128;//red 通道

5,生成一副空白影象

img=Scalar(0)

6,ROI(感興趣區域選擇)

Rect r(10,10,200,200)

Mat src=img(r);

7,Vec3b:對應的三通道的順序是blue,green,red的uchar型別資料

下面給出修改影象三通道畫素值的各種效果，大部分是反色處理

程式碼實現

#include <opencv2\core\core.hpp>
#include <opencv2\imgcodecs.hpp>
#include <opencv2\opencv.hpp>
#include <opencv2\highgui\highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;
int main(int argc, char** args)
{
	Mat image = imread("test.jpg");
	if (image.empty())
	{
		cout << "不能載入影象..." << std::endl;
		return -1;
	}

	Mat dst;
	cvtColor(image, dst, CV_BGR2GRAY);

	int height = image.rows;
	int width = image.cols;
	int channels = image.channels();
	printf("height=%d,width=%d channels=%d",height,width,channels);


	for (int row = 0; row < height;row++)
	{
		for (int col = 0; col < width;col++)
		{
			if (channels==3)
			{
				//image.at<Vec3b>(row, col)[0] = 0;//blue 通道
				//image.at<Vec3b>(row, col)[1] = 0;//green 通道
				//image.at<Vec3b>(row, col)[2] = 255 - image.at<Vec3b>(row, col)[2];// red 通道

				//image.at<Vec3b>(row, col)[0] = 255 - image.at<Vec3b>(row, col)[0];//blue 通道
				//image.at<Vec3b>(row, col)[1] = 255 - image.at<Vec3b>(row, col)[1];//green 通道
				//image.at<Vec3b>(row, col)[2] = 255 - image.at<Vec3b>(row, col)[2];// red 通道

				image.at<Vec3b>(row, col)[0] = 0;//blue 通道
				image.at<Vec3b>(row, col)[1] = 255 - image.at<Vec3b>(row, col)[1];//green 通道
				image.at<Vec3b>(row, col)[2] = 0;// red 通道

				//image.at<Vec3b>(row, col)[1] = 0;//green 通道
				//image.at<Vec3b>(row, col)[2] = 0;// red 通道

			}
			//else if (channels==1)
			//{
			//	dst.at<uchar>(row, col) = 255 - dst.at<uchar>(row, col);
			//}
		}
	}
	namedWindow("輸出影象-2", CV_WINDOW_AUTOSIZE);
	imshow("輸出影象-2", image);
	waitKey(0);
	return 0;
}