CODEWITHSUNDEEP
c++opencv
Kunal Sonone
Kunal Sonone

Reputation: 43

OpenCV Camera Issue:

I have completed the code in opencv for camera interfacing with raspberry pi. I have made the camera.h file, which I am including in my source file. It is working properly. But, in my main program I need the frame which I have capture in capture_image() function.

I want to return the frame at the end of my function capture_image( )

Here is my code:

#include<opencv2/opencv.hpp>  
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <stdio.h>

using namespace cv 
using namespace std;

int n = 0;

static char cam_image[200];

int capture_image() {

VideoCapture capture(2); //try to open string, this will attempt to open it as a video file or image sequence
if (!capture.isOpened()) //if this fails, try to open as a video camera, through the use of an integer param
    capture.open(2);
        if (!capture.isOpened()) {
    cerr << "Failed to open the video device, video file or image sequence!\n" << endl;
    //help(av);
    return 1;
         }
    string window_name = "Reference Image";
        namedWindow(window_name, CV_WINDOW_KEEPRATIO); //resizable window;
    Mat frame;

    capture >> frame;
        if (frame.empty());
    imshow(window_name, frame);
    waitKey(30);
    sprintf(cam_image,"filename%.3d.jpg",n++);
    imwrite(cam_image,frame);
    cout << "Saved " << cam_image << endl;

    return 0;// Actually I want return (frame)
}

the Error:

    camera.h: In function ‘int capture_image()’:
    camera.h:34:17: error: invalid conversion from ‘cv::Mat*’ to ‘int’ [-fpermissive]
    camera.h:24:13: warning: address of local variable ‘frame’ returned [enabled by default]

It is logical that a int function will return int. But, I do not know how to define a cv:: Mat function() . Please help me.

Upvotes: 1

Views: 632

Answers (2)

berak
berak

Reputation: 39796

'return' the Mat in a reference:

int capture_image( Mat & frame)
{
    if ( ! capture.read(frame) )
        return 0;
    return 1;
}



... later:

Mat frame;
int ok = capture_image(frame);
// use frame if ok was true;

Upvotes: 2

Bull
Bull

Reputation: 11941

Just pass the output Mat as a reference and copy the captured frame into. You normally don't want to return the captured frame without copying because it will get overwritten.

int capture_image(cv::Mat& result)   // *** pass output Mat as reference
{

    VideoCapture capture(2); //try to open string, this will attempt to open it as a video file or image sequence
    if (!capture.isOpened()) //if this fails, try to open as a video camera, through the use of an integer param
        capture.open(2);
    if (!capture.isOpened()) {
        cerr << "Failed to open the video device, video file or image sequence!\n" << endl;
       //help(av);
       return 1;
    }
    string window_name = "Reference Image";
    namedWindow(window_name, CV_WINDOW_KEEPRATIO); //resizable window;

    Mat frame;

    capture >> frame;
    if (!frame.empty())
    {
         frame.copyTo(result);    // *** copy captured frame into output Mat
    }
    imshow(window_name, frame);
    waitKey(30);
    sprintf(cam_image,"filename%.3d.jpg",n++);
    imwrite(cam_image,frame);
    cout << "Saved " << cam_image << endl;

    return 0;// Success
}

Upvotes: 2

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