创建Mat对象

Mat像素点的存储方法
Mat的数据类型

CV_8U  - 8bit unsigned integers(0 ~ 255)            8-bit unsigned integer (uchar)
CV_8S  - 8bit signed integers(-128 ~ 127)             8-bit signed integer(schar)
CV_16U - 16bit unsigned integers(0 ~ 65535)            16-bit unsigned integer(ushort)
CV_16S - 16bit signed integers(-32768 ~ 32767)        16-bit signed integer(short)
CV_32S - 32bit signed integers(-2147483648 ~ 2147483647)    32-bit signed integers(int)
CV_32F - 32bit floating-point numbers()                32-bit floating-point number(float)
CV_64F - 64bit floating-point numbers()                64-bit floating-point number(double)

Mat中一个数据（像素）点的格式的定义方式：
CV_[The number of bits per item][Signed or Unsigned][Type Prefix][The channel number]

显式创建Mat对象
1.构造函数创建
    Mat M(3, 2, CV_8UC3, Scalar(0, 0, 255));
2.create函数创建
    Mat M;
    M.create(4, 4, CV_8UC(2));
    使用create函数，无法初始化，如果新的需求跟原来的内存块不匹配，他才会重新分配内存区域，可以减少开辟内存的动作，提升效率

void demo3()
{
	//创建二维矩阵
	Mat M(3, 2, CV_8UC3, Scalar(0, 0, 255));
	cout << "M = " << endl << M << endl;
	//创建三维矩阵
	int sz[3] = { 2, 2, 2 };
	Mat L(3, sz, CV_8UC(1), Scalar::all(0));
	//不支持二维以上的矩阵输出
}
//使用Mat的create函数，显式的创建Mat对象
void demo4()
{
	Mat M;
	cout << "用create函数显式创建一个4*4矩阵，输出查看初始值" << endl;
	M.create(4, 4, CV_8UC1);
	cout << "M = " << endl << M << endl;

	cout << "修改前两个数据的值，输出修改值后的值" << endl;
	M.ptr<uchar>(0)[0] = 12;
	M.ptr<uchar>(0)[1] = 32;
	cout << "M = " << endl << M << endl;

	cout << "再次调用create函数，创建相同大小的矩阵，查看是否对原来的内存区域做了初始化或者重新开辟" << endl;
	M.create(4, 4, CV_8UC1);
	cout << "M = " << endl << M << endl;

	cout << "再次调用create函数，创建不同大小，创建3*3" << endl;
	M.create(3, 3, CV_8UC1);
	cout << "M = " << endl << M << endl;

	cout << "再次调用create函数，创建5*5" << endl;
	M.create(5, 5, CV_8UC1);
	cout << "M = " << endl << M << endl;
}