ch03 MatOp

import cv2
import numpy as np

def MatOp1():
    img1 = np.empty((0, 0), dtype=np.uint8)  # empty matrix

    img2 = np.zeros((480, 640), dtype=np.uint8)  # unsigned char, 1-channel
    img3 = np.zeros((480, 640, 3), dtype=np.uint8)  # unsigned char, 3-channels
    img4 = np.zeros((480, 640, 3), dtype=np.uint8)  # Size(width, height)

    img5 = np.full((480, 640), 128, dtype=np.uint8)  # initial values, 128
    img6 = np.full((480, 640, 3), (0, 0, 255), dtype=np.uint8)  # initial values, red

    mat1 = np.zeros((3, 3), dtype=np.int32)  # 0's matrix
    mat2 = np.ones((3, 3), dtype=np.float32)  # 1's matrix
    mat3 = np.eye(3, 3, dtype=np.float32)  # identity matrix

    data = np.array([1, 2, 3, 4, 5, 6], dtype=np.float32).reshape(2, 3)
    mat4 = data.copy()

    mat5 = np.array([[1, 2, 3], [4, 5, 6]], dtype=np.float32)
    mat6 = np.array([[1, 2, 3], [4, 5, 6]], dtype=np.uint8)

    mat4 = np.zeros((256, 256, 3), dtype=np.uint8)  # uchar, 3-channels
    mat5 = np.zeros((4, 4), dtype=np.float32)  # float, 1-channel

    mat4[:, :] = (255, 0, 0)
    mat5[:, :] = 1.0

def MatOp2():
    img1 = cv2.imread("D:\\projects\\SampleCode\\006939-master\\ch03\\MatOp\\dog.bmp")

    img2 = img1
    img3 = img1

    img4 = img1.copy()
    img5 = img1.copy()

    img1[:, :] = (0, 255, 255)  # yellow

    cv2.imshow("img1", img1)
    cv2.imshow("img2", img2)
    cv2.imshow("img3", img3)
    cv2.imshow("img4", img4)
    cv2.imshow("img5", img5)

    cv2.waitKey()
    cv2.destroyAllWindows()

def MatOp3():
    img1 = cv2.imread("D:\\projects\\SampleCode\\006939-master\\ch03\\MatOp\\cat.bmp")

    if img1 is None:
        print("Image load failed!")
        return

    img2 = img1[120:360, 220:560]
    img3 = img1[120:360, 220:560].copy()

    img2[:] = ~img2

    cv2.imshow("img1", img1)
    cv2.imshow("img2", img2)
    cv2.imshow("img3", img3)

    cv2.waitKey()
    cv2.destroyAllWindows()

def MatOp4():
    mat1 = np.zeros((3, 4), dtype=np.uint8)

    for j in range(mat1.shape[0]):
        for i in range(mat1.shape[1]):
            mat1[j, i] += 1

    for j in range(mat1.shape[0]):
        p = mat1[j]
        for i in range(mat1.shape[1]):
            p[i] += 1

    mat1 = mat1 + 1

    print("mat1:\n", mat1)

def MatOp5():
    img1 = cv2.imread("D:\\projects\\SampleCode\\006939-master\\ch03\\MatOp\\lenna.bmp")

    print("Width:", img1.shape[1])
    print("Height:", img1.shape[0])
    print("Channels:", img1.shape[2])

    if img1.ndim == 2:
        print("img1 is a grayscale image.")
    elif img1.ndim == 3:
        print("img1 is a truecolor image.")

    data = np.array([2.0, 1.414, 3.0, 1.732], dtype=np.float32).reshape(2, 2)
    mat1 = data
    print("mat1:\n", mat1)

def MatOp6():
    data = np.array([1, 1, 2, 3], dtype=np.float32).reshape(2, 2)
    mat1 = data
    print("mat1:\n", mat1)

    mat2 = np.linalg.inv(mat1)
    print("mat2:\n", mat2)

    print("mat1.t():\n", mat1.T)
    print("mat1 + 3:\n", mat1 + 3)
    print("mat1 + mat2:\n", mat1 + mat2)
    print("mat1 * mat2:\n", np.matmul(mat1, mat2))

def MatOp7():
    img1 = cv2.imread("D:\\projects\\SampleCode\\006939-master\\ch03\\MatOp\\lenna.bmp", cv2.IMREAD_GRAYSCALE)

    img1f = img1.astype(np.float32)

    data1 = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], dtype=np.uint8).reshape(3, 4)
    mat1 = data1
    mat2 = mat1.reshape(1, -1)

    print("mat1:\n", mat1)
    print("mat2:\n", mat2)

    mat1 = np.resize(mat1, (5, mat1.shape[1]))
    print("mat1:\n", mat1)

    mat3 = np.ones((1, 4), dtype=np.uint8) * 255
    mat1 = np.vstack([mat1, mat3])
    print("mat1:\n", mat1)

if __name__ == "__main__":
    MatOp1()
    MatOp2()
    MatOp3()
    MatOp4()
    MatOp5()
    MatOp6()
    MatOp7()

---

// C++ code
#include "opencv2/opencv.hpp"
#include <iostream>

using namespace cv;
using namespace std;

void MatOp1();
void MatOp2();
void MatOp3();
void MatOp4();
void MatOp5();
void MatOp6();
void MatOp7();

int main()
{
	MatOp1();
	MatOp2();
	MatOp3();
	MatOp4();
	MatOp5();
	MatOp6();
	MatOp7();

	return 0;
}

void MatOp1()
{
	Mat img1; 	// empty matrix

	Mat img2(480, 640, CV_8UC1);		// unsigned char, 1-channel
	Mat img3(480, 640, CV_8UC3);		// unsigned char, 3-channels
	Mat img4(Size(640, 480), CV_8UC3);	// Size(width, height)

	Mat img5(480, 640, CV_8UC1, Scalar(128));		// initial values, 128
	Mat img6(480, 640, CV_8UC3, Scalar(0, 0, 255));	// initial values, red

	Mat mat1 = Mat::zeros(3, 3, CV_32SC1);	// 0's matrix
	Mat mat2 = Mat::ones(3, 3, CV_32FC1);	// 1's matrix
	Mat mat3 = Mat::eye(3, 3, CV_32FC1);	// identity matrix

	float data[] = { 1, 2, 3, 4, 5, 6 };
	Mat mat4(2, 3, CV_32FC1, data);

	Mat mat5 = (Mat_<float>(2, 3) << 1, 2, 3, 4, 5, 6);
	Mat mat6 = Mat_<uchar>({2, 3}, { 1, 2, 3, 4, 5, 6 });

	mat4.create(256, 256, CV_8UC3);	// uchar, 3-channels
	mat5.create(4, 4, CV_32FC1);	// float, 1-channel

	mat4 = Scalar(255, 0, 0);
	mat5.setTo(1.f);
}

void MatOp2()
{
	Mat img1 = imread("dog.bmp");

	Mat img2 = img1;
	Mat img3;
	img3 = img1;

	Mat img4 = img1.clone();
	Mat img5;
	img1.copyTo(img5);

	img1.setTo(Scalar(0, 255, 255));	// yellow

	imshow("img1", img1);
	imshow("img2", img2);
	imshow("img3", img3);
	imshow("img4", img4);
	imshow("img5", img5);

	waitKey();
	destroyAllWindows();
}

void MatOp3()
{
	Mat img1 = imread("cat.bmp");

	if (img1.empty()) {
		cerr << "Image load failed!" << endl;
		return;
	}

	Mat img2 = img1(Rect(220, 120, 340, 240));
	Mat img3 = img1(Rect(220, 120, 340, 240)).clone();

	img2 = ~img2;

	imshow("img1", img1);
	imshow("img2", img2);
	imshow("img3", img3);

	waitKey();
	destroyAllWindows();
}

void MatOp4()
{
	Mat mat1 = Mat::zeros(3, 4, CV_8UC1);

	for (int j = 0; j < mat1.rows; j++) {
		for (int i = 0; i < mat1.cols; i++) {
			mat1.at<uchar>(j, i)++;
		}
	}

	for (int j = 0; j < mat1.rows; j++) {
		uchar* p = mat1.ptr<uchar>(j);
		for (int i = 0; i < mat1.cols; i++) {
			p[i]++;
		}
	}

	for (MatIterator_<uchar> it = mat1.begin<uchar>(); it != mat1.end<uchar>(); ++it) {
		(*it)++;
	}

	cout << "mat1:\n" << mat1 << endl;
}

void MatOp5()
{
	Mat img1 = imread("lenna.bmp");

	cout << "Width: " << img1.cols << endl;
	cout << "Height: " << img1.rows << endl;
	cout << "Channels: " << img1.channels() << endl;

	if (img1.type() == CV_8UC1)
		cout << "img1 is a grayscale image." << endl;
	else if (img1.type() == CV_8UC3)
		cout << "img1 is a truecolor image." << endl;

	float data[] = { 2.f, 1.414f, 3.f, 1.732f };
	Mat mat1(2, 2, CV_32FC1, data);
	cout << "mat1:\n" << mat1 << endl;
}

void MatOp6()
{
	float data[] = { 1, 1, 2, 3 };
	Mat mat1(2, 2, CV_32FC1, data);
	cout << "mat1:\n" << mat1 << endl;

	Mat mat2 = mat1.inv();
	cout << "mat2:\n" << mat2 << endl;

	cout << "mat1.t():\n" << mat1.t() << endl;
	cout << "mat1 + 3:\n" << mat1 + 3 << endl;
	cout << "mat1 + mat2:\n" << mat1 + mat2 << endl;
	cout << "mat1 * mat2:\n" << mat1 * mat2 << endl;
}

void MatOp7()
{
	Mat img1 = imread("lenna.bmp", IMREAD_GRAYSCALE);

	Mat img1f;
	img1.convertTo(img1f, CV_32FC1);

	uchar data1[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
	Mat mat1(3, 4, CV_8UC1, data1);
	Mat mat2 = mat1.reshape(0, 1);

	cout << "mat1:\n" << mat1 << endl;
	cout << "mat2:\n" << mat2 << endl;

	mat1.resize(5, 100);
	cout << "mat1:\n" << mat1 << endl;

	Mat mat3 = Mat::ones(1, 4, CV_8UC1) * 255;
	mat1.push_back(mat3);
	cout << "mat1:\n" << mat1 << endl;
}

C++ Code 출처 : OpenCV 4로 배우는 컴퓨터 비전과 머신 러닝 - 황선규 저

---

mat1:
 [[3 3 3 3]
 [3 3 3 3]
 [3 3 3 3]]
Width: 512
Height: 512
Channels: 3
img1 is a truecolor image.
mat1:
 [[2.    1.414]
 [3.    1.732]]
mat1:
 [[1. 1.]
 [2. 3.]]
mat2:
 [[ 3. -1.]
 [-2.  1.]]
mat1.t():
 [[1. 2.]
 [1. 3.]]
mat1 + 3:
 [[4. 4.]
 [5. 6.]]
mat1 + mat2:
 [[4. 0.]
 [0. 4.]]
mat1 * mat2:
 [[1. 0.]
 [0. 1.]]
mat1:
 [[ 1  2  3  4]
 [ 5  6  7  8]
 [ 9 10 11 12]]
mat2:
 [[ 1  2  3  4  5  6  7  8  9 10 11 12]]
mat1:
 [[ 1  2  3  4]
 [ 5  6  7  8]
 [ 9 10 11 12]
 [ 1  2  3  4]
 [ 5  6  7  8]]
mat1:
 [[  1   2   3   4]
 [  5   6   7   8]
 [  9  10  11  12]
 [  1   2   3   4]
 [  5   6   7   8]
 [255 255 255 255]]