Opencv learning notes -day3 (mat object and creation related operations mat:: clone(), mat:: copyto(), mat:: zeros(), mat:: ones(), scalar()...)

day3-Mat Object and creation

Mat The basic operation of class

Mat class ：Mat::clone(),Mat::copyTo(),Mat::zeros(),Mat::ones(),Scalar()

One , Copy

function ：

1. “=” Shallow copy

Shallow copy - Do not copy data but create matrix headers , Data sharing

example 1

Mat a = imread("1.jpg");

2. Mat::clone

clone It's a complete deep copy , Apply for new space in memory

// Definition 
Mat Mat::clone() const
{
    
    Mat m;
    copyTo(m);
    return m;
}

example 2

Mat m1 = image.clone();
//clone  It's a complete deep copy , Apply for new space in memory , And image Independent 

3. Mat::copyTo

// Definition 
void GpuMat::copyTo(OutputArray dst, InputArray mask) const
{
    
    copyTo(dst, mask, Stream::Null());
}

OpenCV in image.copyTo() There are two forms ：

1、image.copyTo(imageROI), The effect is to turn image Paste your content into imageROI;

2、image.copyTo(imageROI,mask), The effect is to turn mask and image After overlapping, put mask The pixel value in is 0（black） The point corresponding to image The point in the becomes transparent , And keep other points .

mask： The mask . The mask is made by 0 and 1 Make up a binary image . When a mask is applied to a function ,1 Value area is processed , Shielded 0 The value area is not included in the calculation . By the specified data value 、 Data range 、 Finite or infinite value 、 Region of interest and annotation file to define image mask , Any combination of the above options can also be used as input to establish a mask .

example 3

image.copyTo(m2);// hold image Copy the contents of to m2 in 

Two , Create a blank image

function ：

1. Mat::zeros() Returns an array of zeros of the specified size and type

   Mat::ones() Returns the specified size and type 1 Array of

// Definition 
static MatExpr zeros(Size size, int type);
static MatExpr ones(Size size, int type);

type Can be any predefined type , The structure of the predefined types is as follows :
CV_<bit_depth>(S|U|F)C<number_of_channels>
1）bit_depth— Number of bits — representative 8bite,16bites,32bites,64bites— Let's give you an example – for instance , Such as
If you create a store now – Grayscale image of Mat object , The size of this image is wide 100, high 100, that , Now this grayscale image has 10000 Pixels , The memory space occupied by each pixel is 8bite,8 position – So it corresponds to CV_8

2）S|U|F
S– representative —signed int— There's symbolic plastic
U– representative –unsigned int– Unsigned shaping
F– representative –float--------- Single precision floating point

3）C<number_of_channels>
representative — The number of channels in a picture , such as :
1– Grayscale picture –grayImg— yes – Single channel image
2–RGB Color images --------- yes –3 Channel image
3– belt Alph The tunnel RGB Images – yes --4 Channel image

example 4

Mat m3 = Mat::zeros(Size(8, 8), CV_8UC1);
// Create a matrix ;CV_8UC1 8-bit unsigned single channel  CV_8UC1 single channel 
// Initialize to 1  At this time, only single channel can be selected  
//if Use 3 If the channel looks at the complete results below, there will be errors - Only the first channel is initialized to 1
Mat m3 = Mat::ones(Size(8, 8), CV_8UC1);//8*8 8 Bit unsigned single channel 
// Initialize to 1, Use 3 passageway 
Mat m3 = Mat::ones(Size(8, 8), CV_8UC3);//8*8 8 Bit unsigned 3 passageway 

2. Mat::cols Row number

   Mat::rows Number of columns

   Mat::channels The channel number

example 5

std::cout << "width: " << m3.cols << std::endl;// Output width 
	std::cout << "height: " <<m3.rows << std::endl;// Output width 
	std::cout << "channels: " << m3.channels()<< std::endl;// Number of output channels 

Code

quickopencv.h

#pragma once

#include <opencv2\highgui.hpp>

#include <opencv2\imgproc.hpp>

using namespace cv;
// Defining classes 
class QuickDemo{
    
public:
	void colorSpace_Demo(Mat &image);// Color space conversion function 2021-12-24
	void mat_creation_demo(Mat &image);//Mat Object and creation 2021-12-27
};

OpencvTest.cpp

#include <iostream>
#include <opencv2\highgui.hpp>
#include <opencv2\imgproc.hpp>
#include<quickopencv.h>

using namespace cv;
using namespace std;


int main()
{
    
	Mat scr = imread("D:\\ Study \\OpenCV Study \\pictures\\image\\1.jpg");// Open a picture 
	if (!scr.data == 1)// Sentenced to empty 
		return -1;
	namedWindow(" window 1", WINDOW_NORMAL);// establish  WINDOW_FREERATIO window 
	imshow(" window 1",scr);// Show in the created window 
	QuickDemo qd;
	//qd.colorSpace_Demo(scr);// Color conversion 
	//waitKey(0);// Time delay  0-> Constant delay  1-> Time delay 1ms
	qd.mat_creation_demo(scr);//Mat Class 
	waitKey(0);
	return 0;

QuickDemo.cpp

#include <opencv2\highgui.hpp>

#include <opencv2\imgproc.hpp>

#include<quickopencv.h>

#include <iostream>
//  The name of the function ：void QuickDemo::mat_creation_demo(Mat &image)
//  Functional specifications ：Mat Object and creation 
//  Parameter description ：Mat &image
//  The function returns ： nothing 
//  Modification time ：2021 year 12 month 29 Japan 
//  To prepare   notes ：
void QuickDemo::mat_creation_demo(Mat &image)
{
    
	// Create a blank image  
	//8*8 8 Bit unsigned 1 passageway   All initialized to 0
	Mat m3 = Mat::zeros(Size(8, 8), CV_8UC1);// matrix ;size：8*8 CV_8UC1： 8-bit unsigned single channel   Initialize to 0--- Show results 1 
	//Mat m3 = Mat::zeros(Size(8, 8), CV_8UC3);//CV_8UC3 Octet unsigned 3 passageway -- Show results 2
	
	// Initialize to 1  At this time, only single channel can be selected  if Use 3 The channel will have errors in the following results 
	//Mat m3 = Mat::ones(Size(8, 8), CV_8UC1);//szie：8*8 CV_8UC1：8 Bit unsigned single channel   Initialize to 0-- Show results 3
	//Mat m3 = Mat::ones(Size(8, 8), CV_8UC3);//size：8*8 CV_8UC3：8 Bit unsigned 3 passageway   Initialize to 1-- Show results 4  Only the first channel can be initialized 
	std::cout << "width: " << m3.cols << std::endl;// Output width 
	std::cout << "height: " <<m3.rows << std::endl;// Output width 
	std::cout << "channels: " << m3.channels()<< std::endl;// Number of output channels 
	std::cout << m3 << std::endl;// Output m3
}

Show results 1

Show results 2

Show results 3

Show results 4- Only the first channel can be initialized

3、 ... and , Assignment operation

function ：

1. Scalar() Assign values to three channels

// Definition 
Scalar_<_Tp>::Scalar_(_Tp v0, _Tp v1, _Tp v2, _Tp v3)
{
    
    this->val[0] = v0;
    this->val[1] = v1;
    this->val[2] = v2;
    this->val[3] = v3;
}

example 6

m4 = Scalar(127,127,127);// to 3 Each channel is assigned a value   grayscale  
//127 Is the grayscale value 
m4 = Scalar(255, 0, 0);
//300*300 3 The grayscale of the channel (127,127,127),
// Blue (255,0,0), green (0,255,0), yellow (0,0,255)

Code

quickopencv.h

#pragma once

#include <opencv2\highgui.hpp>

#include <opencv2\imgproc.hpp>

using namespace cv;
// Defining classes 
class QuickDemo{
    
public:
	void colorSpace_Demo(Mat &image);// Color space conversion function 2021-12-24
	void mat_creation_demo(Mat &image);//Mat Object and creation 2021-12-27
};

OpencvTest.cpp

#include <iostream>
#include <opencv2\highgui.hpp>
#include <opencv2\imgproc.hpp>
#include<quickopencv.h>

using namespace cv;
using namespace std;


int main()
{
    
	Mat scr = imread("D:\\ Study \\OpenCV Study \\pictures\\image\\1.jpg");// Open a picture 
	if (!scr.data == 1)// Sentenced to empty 
		return -1;
	namedWindow(" window 1", WINDOW_NORMAL);// establish  WINDOW_FREERATIO window 
	imshow(" window 1",scr);// Show in the created window 
	QuickDemo qd;
	//qd.colorSpace_Demo(scr);// Color conversion 
	//waitKey(0);// Time delay  0-> Constant delay  1-> Time delay 1ms
	qd.mat_creation_demo(scr);//Mat Class 
	waitKey(0);
	return 0;

QuickDemo.cpp

void QuickDemo::mat_creation_demo(Mat &image)
{
    
	// Assignment operation 
	Mat m4=Mat::zeros(Size(300,300),CV_8UC3);
	//m4 = 127;// Only the first channel can be assigned at this time  127 It's grayscale 
	//-- Show results 5
	//Scalar() function 
	m4 = Scalar(127,127,127);// to 3 Each channel is assigned a value   grayscale -- result 6
	//m4 = Scalar(255, 0, 0);//300*300 3 The grayscale of the channel (127,127,127), Blue (255,0,0), green (0,255,0), yellow (0,0,255)-- Show results 7
	imshow("m4", m4);// It can be used imshow The output shows  

	//Mat m5 = m4;//m5 Yes m4 //***
	//m5 = Scalar(0, 255, 255);// At this time, the m4 The color of is yellow 
	//imshow("m4",m4);//m4 The output is displayed in yellow -- Show results 8

	std::cout << "width: " << m4.cols << std::endl;// Output width 
	std::cout << "height: " <<m4.rows << std::endl;// Output width 
	std::cout << "channels: " << m4.channels()<< std::endl;// Number of output channels 
	std::cout << m4 << std::endl;// Output m
}

result 5– Only the first channel is assigned

result 6.1– Use Scalar(),3 Each channel is assigned a value

result 6.2–300*300 3 Grayscale image of the channel

Show results 7.1

Show results 7.2

Show results 7.3

Show results 8