Opencv Tutorial

Read Image

cv::Mat cv::imread(const std::string &filename, int flags = IMREAD_COLOR)

enum cv::ImreadModes
{
    IMREAD_UNCHANGED,                       //-1    使图像保持原样输出
    IMREAD_GRAYSCALE,                       //0     把图像转成单通道的灰度图输出
    IMREAD_COLOR ,                          //1     //把图像转成三通道的rgb图输出
    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     //以任何可能的颜色格式读取图像
    IMREAD_LOAD_GDAL,                       //8     //use the gdal driver for loading the image
    IMREAD_REDUCED_GRAYSCALE_2,     //16    //输出单通道灰度图，并且将图像缩小为原来的1/2
    IMREAD_REDUCED_COLOR_2 ,        //17    //输出三通道的rgb图，并且缩小图像到原来的1/2
    IMREAD_REDUCED_GRAYSCALE_4, //32    //单通道  1/4
    IMREAD_REDUCED_COLOR_4 ,        //33    //三通道  1/4
    IMREAD_REDUCED_GRAYSCALE_8, //64        //单通道  1/8
    IMREAD_REDUCED_COLOR_8 ,        //65    //三通道  1/8
    IMREAD_IGNORE_ORIENTATION       //128   //do not rotate the image according to EXIF's orientation flag.
}

demo调用, 源码 1 2 3：

TEST(ReadImage, read_image_test)
{
    std::string filename = GetOpenCVDatasetDirectory() + "/0001_tian_an_man.jpeg";
    ReadImage demo;
    demo.Read(filename);
}

函数使用：

void ReadImage::Read(const std::string& filename)
{
    cv::Mat image = cv::imread(filename);

    if (image.data == nullptr) {
        std::cout << "Load image error." << std::endl;
        exit(-1);
    }

    cv::imshow("Opencv read image", image);
    cv::waitKey(0);
    cv::destroyAllWindows();
}

Footnotes

1

read_image.cpp

2

read_image.h

3

read_image_test.cpp