OpenCV 从标准输入加载图像/视频

Question

我正在尝试使用以下代码从标准输入读取 jpg 图像:

int c,count=0;
vector<uchar> buffer; //buffer for coding

/* for stdin, we need to read in the entire stream until EOF */
while ((c = fgetc(stdin)) != EOF) {
     buffer.push_back(c);
 count++;
}


cout << "Bytes: " << count << endl;
Mat im = imdecode(Mat(buffer),CV_LOAD_IMAGE_COLOR);
cout << "Decoded\n";
namedWindow("image", CV_WINDOW_AUTOSIZE);
imshow("image",im);

cv::waitKey(0);

我在 cmd 中运行:

OpenCVTest < thumb.jpg

这是我得到的:

Bytes: 335
Decoded
OpenCV Error: Bad flag (parameter or structure field) (Unrecognized or unsupported array type) in unknown function, file ..\..\..\src\opencv\modules\core\src\array.cpp, line 2482

这个错误似乎是合理的，因为图像大约有 7 KB，但根据计数器，只读取了 335 个字节。

我做错了什么？

我的最终目标是逐帧从 stdin 读取视频。这可能吗？

非常感谢!

Answer 1

以下从 stdin 逐帧读取 jpeg 序列。示例:

ffmpeg

ffmpeg -i input.mp4 -vcodec mjpeg -f image2pipe -pix_fmt yuvj420p -r 10 -|program.exe

编码器

mencoder input.mp4 -nosound -ovc lavc -lavcopts vcodec=mjpeg -o -|program.exe

curl

curl "http://10.10.201.241/mjpeg/video.cgi&resolution=320x240"|program.exe

代码

#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace cv;

#if defined(_MSC_VER) || defined(WIN32)  || defined(_WIN32) || defined(__WIN32__) \
    || defined(WIN64)    || defined(_WIN64) || defined(__WIN64__)
# include <io.h>
# include <fcntl.h>
# define SET_BINARY_MODE(handle) setmode(handle, O_BINARY)
#else
# define SET_BINARY_MODE(handle) ((void)0)
#endif

#define BUFSIZE 10240
int main ( int argc, char **argv )
{

    SET_BINARY_MODE(fileno(stdin));
    std::vector<char> data;
    bool skip=true;
    bool imgready=false;
    bool ff=false;
    int readbytes=-1;
    while (1)
    {   
        char ca[BUFSIZE];
        uchar c;
        if (readbytes!=0)
        {
            readbytes=read(fileno(stdin),ca,BUFSIZE);
            for(int i=0;i<readbytes;i++)
            {
                c=ca[i];
                if(ff && c==(uchar)0xd8)
                {
                    skip=false;
                    data.push_back((uchar)0xff);
                }
                if(ff && c==0xd9)
                {
                    imgready=true;
                    data.push_back((uchar)0xd9);
                    skip=true;
                }
                ff=c==0xff;
                if(!skip)
                {
                    data.push_back(c);
                }
                if(imgready)
                {
                    if(data.size()!=0)
                    {
                        cv::Mat data_mat(data);
                        cv::Mat frame(imdecode(data_mat,1));

                        imshow("frame",frame);
                        waitKey(1);
                    }else
                    {
                        printf("warning");
                    }
                    imgready=false;
                    skip=true;
                    data.clear();
                }
            }
        }
        else
        {
            throw std::string("zero byte read");
        }
    }
}