一，存储图像

1，存储 imwrite

imwrite("D:/im2.jpg", image2);

第三个参数缺省了。

2，编码格式

jpg是有损压缩，png是无损压缩，如果对图片要求很高的，还是用png好一点。

3，图片位深

32F类型的图片，像这样存下来之后会变成8U的，读取之后也是8U的，

即使再转换成32F的，也可能和原图有差异。

二，读取图像

1，读取 imread

string path = "D:/im2.jpg";
Mat image = imread(path, IMREAD_UNCHANGED);
if (!image.data) {
	cout << "imread fail\n";
	return;
}

第二个参数是ImreadModes类型的枚举，表示读取的通道数

返回的是一个Mat类型的对象。

成员data是uchar的指针，如果读取失败那么指针为空

2，读取类型 ImreadModes

ImreadModes的源代码：

enum ImreadModes {
       IMREAD_UNCHANGED            = -1, //!< If set, return the loaded image as is (with alpha channel, otherwise it gets cropped). Ignore EXIF orientation.
       IMREAD_GRAYSCALE            = 0,  //!< If set, always convert image to the single channel grayscale image (codec internal conversion).
       IMREAD_COLOR                = 1,  //!< If set, always convert image to the 3 channel BGR color image.
       IMREAD_ANYDEPTH             = 2,  //!< If set, return 16-bit/32-bit image when the input has the corresponding depth, otherwise convert it to 8-bit.
       IMREAD_ANYCOLOR             = 4,  //!< If set, the image is read in any possible color format.
       IMREAD_LOAD_GDAL            = 8,  //!< If set, use the gdal driver for loading the image.
       IMREAD_REDUCED_GRAYSCALE_2  = 16, //!< If set, always convert image to the single channel grayscale image and the image size reduced 1/2.
       IMREAD_REDUCED_COLOR_2      = 17, //!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/2.
       IMREAD_REDUCED_GRAYSCALE_4  = 32, //!< If set, always convert image to the single channel grayscale image and the image size reduced 1/4.
       IMREAD_REDUCED_COLOR_4      = 33, //!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/4.
       IMREAD_REDUCED_GRAYSCALE_8  = 64, //!< If set, always convert image to the single channel grayscale image and the image size reduced 1/8.
       IMREAD_REDUCED_COLOR_8      = 65, //!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/8.
       IMREAD_IGNORE_ORIENTATION   = 128 //!< If set, do not rotate the image according to EXIF's orientation flag.
     };

-1 IMREAD_UNCHANGED 表示按照图片本身的通道数

0 IMREAD_GRAYSCALE 表示灰度图像，即单通道

1 IMREAD_COLOR 表示按照3通道

Opencv存图读图