问题
I'm trying to implement a streaming service using OpenCV and sockets. The server side loads a given image and sends it to the client, which receives it through the socket and displays it. I'm having a lot of trouble, though, sending the data of the image and reconstructing it on the client side. This is the code I've made so far:
Image sender:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
using namespace cv;
using namespace std;
void error(const char *msg)
{
perror(msg);
exit(0);
}
int main(int argc, char *argv[])
{
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[256];
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0);
}
portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,
(char *)&serv_addr.sin_addr.s_addr,
server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
error("ERROR connecting");
Mat image;
image = imread(argv[3], CV_LOAD_IMAGE_COLOR);
if(! image.data ) // Check for invalid input
{
cout << "Could not open or find the image" << std::endl ;
return -1;
}
n = write(sockfd,image.data,image.total()*image.channels());
if (n < 0)
error("ERROR writing to socket");
close(sockfd);
namedWindow( "Client", CV_WINDOW_AUTOSIZE );// Create a window for display.
imshow( "Client", image );
waitKey(0);
return 0;
}
Image receiver:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
using namespace cv;
using namespace std;
void error(const char *msg)
{
perror(msg);
exit(1);
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno;
socklen_t clilen;
char buffer[1024];
struct sockaddr_in serv_addr, cli_addr;
int n;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0)
error("ERROR on binding");
listen(sockfd,5);
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,
(struct sockaddr *) &cli_addr,
&clilen);
if (newsockfd < 0)
error("ERROR on accept");
bzero(buffer,1024);
n = read(newsockfd,buffer,1023);
if (n < 0) error("ERROR reading from socket");
Mat image(690,690,CV_8UC3,*buffer);
imwrite("/home/securitas/images/prova.jpg",image);
close(newsockfd);
close(sockfd);
namedWindow( "Server", CV_WINDOW_AUTOSIZE );// Create a window for display.
imshow( "Server", image );
waitKey(0);
return 0;
}
Al I receive on the client side is a black image, nothing else. Any help?
回答1:
Get Mat.data and directly send to the socket, the data order is BGR BGR BGR.... On the receiving side assumes you know the size of image. After receiving just assign the received buffer(BGR BGR... array) to a Mat.
Client:-
Mat frame;
frame = (frame.reshape(0,1)); // to make it continuous
int imgSize = frame.total()*frame.elemSize();
// Send data here
bytes = send(clientSock, frame.data, imgSize, 0))
Server:-
Mat img = Mat::zeros( height,width, CV_8UC3);
int imgSize = img.total()*img.elemSize();
uchar sockData[imgSize];
//Receive data here
for (int i = 0; i < imgSize; i += bytes) {
if ((bytes = recv(connectSock, sockData +i, imgSize - i, 0)) == -1) {
quit("recv failed", 1);
}
}
// Assign pixel value to img
int ptr=0;
for (int i = 0; i < img.rows; i++) {
for (int j = 0; j < img.cols; j++) {
img.at<cv::Vec3b>(i,j) = cv::Vec3b(sockData[ptr+ 0],sockData[ptr+1],sockData[ptr+2]);
ptr=ptr+3;
}
}
回答2:
bytes = send(clientSock, frame.data, imgSize, 0));
This statement is giving error in Visual Studio 12.It say that.. ERROR: argument of type "uchar *" is incompatible with parameter of type "const char *" at ""frame.data"".
回答3:
Buffer overflow. And I am not sure that format and sizes of image are the same -> you should serialize your Mat honestly, something like here.
回答4:
Haris's answer is right and worked for me. However, instead of that server code (constructing image from uchar data), you can also use the shorter form:
int imgSize = img.total()*img.elemSize();
uchar sockData[imgSize];
for (int i = 0; i < imgSize; i += bytes) {
if ((bytes = recv(connectSock, sockData +i, imgSize - i, 0)) == -1)
quit("recv failed", 1);
}
// change the last loop to below statement
Mat img(Size(HEIGHT, WIDTH), CV_8UC3, socketData);
回答5:
In Microsoft Visual Studio 2012, I have a red line under imgSize in sockData[imgSize] saying expression must have a constant value. I then changed int imgSize to const int imgSize. It still shows me the same problem.
Mat img = Mat::zeros(100,100, CV_8UC3);
const int imgSize = img.total()*img.elemSize();
uchar sockData[imgSize];
来源：https://stackoverflow.com/questions/20314524/c-opencv-image-sending-through-socket