一：OpenCV图片读取与写入文件帮助文档

1.函数名：imread
定义：
Mat imread( const String& filename, int flags = IMREAD_COLOR );
def imread(filename, flags=None)
参数：
filename：文件名
flags：读取标识，枚举类型，
可以取以下值

enum ImreadModes {
       IMREAD_UNCHANGED  = -1, //!< If set, return the loaded image as is (with alpha channel, otherwise it gets cropped).
       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.
     };

作用：读取图像，flags参数取“0”或“1”比较常见，取“0”是得到的图像是灰度图像。取“1”得到三通道彩色图像。

python code
import cv2
#读取指定图片灰度图片
gray_image=cv2.imread(img_path,0)

#读取指定图片3通道
org_image=cv2.imread(img_path,1)

#-------------------------------------
#C code
#include 
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
    //根据图像文件路径和文件名读取图像文件
    Mat src = imread("e:/TestImage/bike.jpg",1);
    //创建一个图像显示窗口
    namedWindow("src", 0);
    //显示图像
    imshow("src", src);
    //等待用户按键触发,如果没有该语句，窗口显示图像之后就自动关闭。
    waitKey(0);
    return 0;
}

2.函数名：imwrite
定义：
bool imwrite( const String& filename, InputArray img, const std::vector& params = std::vector());
def imwrite(filename, img, params=None)
参数：
filename：文件名
img：要保存的图像
params：表示为特定格式保存的参数编码，通常直接采用默认值。
作用：保存图像。

python code:
#保存图片至文件
cv2.imwrite("xxx", image)

#---------------------------
C code：
#include 
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
    Mat src = imread("e:/TestImage/bike.jpg", 1);
    namedWindow("src", 0);
    imshow("src", src);
    imwrite("e:/TestImage/bike_write.bmp", src);
    waitKey(0);
    return 0;
}

如果保存文件路径有中文可以使用一下方法来保存:

cv2.imencode('.jpg', image)[1].tofile(save_img_path)

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