openCV贾志刚老师视频学习-4

目录

读写图像

读写像素

修改像素值

Vec3b与Vec3F

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读写图像

imread 可以指定加载为灰度或者RGB图像

Imwrite 保存图像文件，类型由扩展名决定

读写像素

读一个GRAY像素点的像素值

（CV_8UC1） Scalar intensity = img.at<uchar>(y, x);

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

读一个RGB像素点的像素值

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

float blue = intensity.val[0];

float green = intensity.val[1];

float red = intensity.val[2];

修改像素值

灰度图像

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

RGB三通道图像

img.at<Vec3b>(y,x)[0]=128; // blue

img.at<Vec3b>(y,x)[1]=128; // green

img.at<Vec3b>(y,x)[2]=128; // red

空白图像赋值

img = Scalar(0);

ROI选择

Rect r(10, 10, 100, 100);

Mat smallImg = img(r);

Vec3b与Vec3F

Vec3b对应三通道的顺序是blue、green、red的uchar类型数据。

Vec3f对应三通道的float类型数据

把CV_8UC1转换到CV32F1实现如下： src.convertTo(dst, CV_32F);

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

using namespace std;
using namespace cv;

int main(int argc, char** argv) {
	Mat src;
	src = imread("D:/vcprojects/images/test.png");
	if (src.empty()) {
		cout << "could not load image..." << endl;
		return -1;
	}
	namedWindow("input", CV_WINDOW_AUTOSIZE);
	imshow("input", src);

	/*Mat dst;
	dst = Mat(src.size(), src.type());
	dst = Scalar(127, 0, 255);
	namedWindow("output", CV_WINDOW_AUTOSIZE);
	imshow("output", dst);*/
	Mat dst;
	//src.copyTo(dst);
	namedWindow("output", CV_WINDOW_AUTOSIZE);

	cvtColor(src, dst, CV_BGR2GRAY);
	printf("input image channels : %d\n", src.channels());
	printf("output image channels : %d\n", dst.channels());

	int cols = dst.cols;
	int rows = dst.rows;

	printf("rows : %d cols : %d\n", rows, cols);
	const uchar* firstRow = dst.ptr<uchar>(0);
	printf("fist pixel value : %d\n", *firstRow);

	Mat M(100, 100, CV_8UC1, Scalar(127));
	//cout << "M =" << endl << M << endl;

	Mat m1;
	m1.create(src.size(), src.type());
	m1 = Scalar(0, 0, 255);

	Mat csrc;
	Mat kernel = (Mat_<char>(3, 3) << 0, -1, 0, -1, 5, -1, 0, -1, 0);
	filter2D(src, csrc, -1, kernel);

	Mat m2 = Mat::eye(2, 2, CV_8UC1);
	cout << "m2 =" << endl << m2 << endl;

	imshow("output", m2);
	waitKey(0);
	return 0;
}