opencv学习-第四节：图像对象的创建与赋值

Posted 2021-06-26 殇堼

知识点: OpenCV中图像对象创建与赋值
C+ +中Mat对象与创建
Python中Numpy数组对象

1.Mat基本结构

数据部分是像素集的一个集合
头部：图像的属性，尺寸、通道数、

2.Mat的赋值方法

一共三种方法：1.克隆 2.复制 3.赋值

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
//创建一个空白图像，zeros表示将所有像素点初始化为0，长宽为8*8，1表示单通道
	Mat m3 = Mat::zeros(Size(8, 8), CV_8UC1);
	std::cout << m3 << std::endl;
	}

单通道是一位，等于八个字节。

三通道是3位，等于24个字节。

如何操作mat，如何遍历访问它每一个像素点
如何创建一个空的图像（mat）

3.获取图像的宽度、长度和通道数

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);

	Mat m3 = Mat::zeros(Size(8, 8), CV_8UC3);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	}

4.所有像素点初始化为1

以下代码将所有像素点初始化为1，注意通道数要为1，如果是3的话，第一个通道是1，其余为0

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);

	Mat m3 = Mat::ones(Size(8, 8), CV_8UC1);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	}

5.将第一个通道自定义一个数值

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(8, 8), CV_8UC3);
	m3 = 125;
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	}

6.将三个通道都赋值

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(8, 8), CV_8UC3);
	m3 = Scalar(125,125,125);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	}

7.显示创建的图像-imshow(“创建图像”, m3);

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(8, 9), CV_8UC3);
	m3 = Scalar(125,125,125);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	imshow("创建图像", m3);
	}

左上角即为刚刚创建好的图像（m3）
其三个通道的像素值都是125。

8.创建有颜色的图像

蓝色：

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(400, 400), CV_8UC3);
	m3 = Scalar(255,0,0);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	imshow("创建图像", m3);
	}

红色：

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(300,300), CV_8UC3);
	m3 = Scalar(0,0,255);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	imshow("创建图像", m3);
	}

绿色

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(300,300), CV_8UC3);
	m3 = Scalar(0,255,0);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	imshow("创建图像", m3);
	}

8.定义一个新的图像窗口，克隆或是复制旧图像赋值给新图像

方法1：克隆

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(300,300), CV_8UC3);
	m3 = Scalar(0,255,0);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	Mat m4 = m3.clone();//m4为m3的克隆体
	m4 = Scalar(0, 255, 255); //在克隆的基础上更改像素值。
	imshow("图像3", m3);//命名并显示两张图片m3、m4
	imshow("图像4", m4);
		}

方法2：复制

void QuickDemo::mat_creation_demo(Mat &image) {
	Mat m1, m2; 
	m1 = image.clone();
	image.copyTo(m2);
	Mat m3 = Mat::ones(Size(300,300), CV_8UC3);
	m3 = Scalar(0,255,0);
	std::cout << "width: " << m3.cols << "height: " << m3.rows << "channels: "<<m3.channels()<< std::endl;
	std::cout << m3 << std::endl;
	Mat m4;
	m3.copyTo(m4);//m4为m3的克隆体
	m4 = Scalar(0, 255, 255); //在克隆的基础上更改像素值。
	imshow("图像3", m3);//命名并显示两张图片m3、m4
	imshow("图像4", m4);
		}

（3）OpenCV 4 学习之图像创建与赋值